diff --git a/README.md b/README.md
index 12f8184..fbaf7d3 100644
--- a/README.md
+++ b/README.md
@@ -268,8 +268,8 @@ env.Preprocess(target, source)
 env.Preprocess("module-preprocessed.cc", "module.cc")
 ```
 
-The Preprocess builder invokes either ${CC} or ${CXX} (depending on if the
-source contains an extension in ${CXXSUFFIX} or not) and writes the
+The Preprocess builder invokes either `${CC}` or `${CXX}` (depending on if the
+source contains an extension in `${CXXSUFFIX}` or not) and writes the
 preprocessed output to the target file.
 
 #### Program
diff --git a/lib/rscons.rb b/lib/rscons.rb
index 80a5090..de324d2 100644
--- a/lib/rscons.rb
+++ b/lib/rscons.rb
@@ -15,6 +15,8 @@ require_relative "rscons/builders/program"
 
 # Namespace module for rscons classes
 module Rscons
+  # Names of the default builders which will be added to all newly created
+  # {Environment} objects.
   DEFAULT_BUILDERS = [
     :CFile,
     :Disassemble,
@@ -24,9 +26,10 @@ module Rscons
     :Program,
   ]
 
+  # Class to represent a fatal error while building a target.
   class BuildError < RuntimeError; end
 
-  # Remove all generated files
+  # Remove all generated files.
   def self.clean
     cache = Cache.instance
     # remove all built files
@@ -43,20 +46,27 @@ module Rscons
     cache.clear
   end
 
-  # Return whether the given path is an absolute filesystem path or not
-  # @param path [String] the path to examine
+  # Return whether the given path is an absolute filesystem path.
+  #
+  # @param path [String] the path to examine.
+  #
+  # @return [Boolean] Whether the given path is an absolute filesystem path.
   def self.absolute_path?(path)
     path =~ %r{^(/|\w:[\\/])}
   end
 
   # Return a new path by changing the suffix in path to suffix.
-  # @param path [String] the path to alter
-  # @param suffix [String] the new filename suffix
+  #
+  # @param path [String] The path to alter.
+  # @param suffix [String] The new filename suffix, e.g. ".exe".
+  #
+  # @return [String] New path.
   def self.set_suffix(path, suffix)
     path.sub(/\.[^.]*$/, suffix)
   end
 
   # Return the system shell and arguments for executing a shell command.
+  #
   # @return [Array<String>] The shell and flag.
   def self.get_system_shell
     @@shell ||=
diff --git a/lib/rscons/build_target.rb b/lib/rscons/build_target.rb
index 33fb060..23ddcee 100644
--- a/lib/rscons/build_target.rb
+++ b/lib/rscons/build_target.rb
@@ -18,6 +18,8 @@ module Rscons
     # Manually record a given target as depending on the specified files.
     #
     # @param user_deps [Array<String>] Dependency files.
+    #
+    # @return [void]
     def depends(*user_deps)
       @env.depends(@target, *user_deps)
     end
diff --git a/lib/rscons/builder.rb b/lib/rscons/builder.rb
index 3af964a..241189f 100644
--- a/lib/rscons/builder.rb
+++ b/lib/rscons/builder.rb
@@ -7,14 +7,17 @@ module Rscons
   # Class to hold an object that knows how to build a certain type of file.
   class Builder
     # Return the name of the builder.
+    #
     # If not overridden this defaults to the last component of the class name.
     def name
       self.class.name.split(":").last
     end
 
-    # Return a set of default variable values for the Environment to use
-    # unless the user overrides any.
+    # Return a set of default construction variables for the builder.
+    #
     # @param env [Environment] The Environment.
+    #
+    # @return [Hash] Default construction variables.
     def default_variables(env)
       {}
     end
@@ -39,16 +42,33 @@ module Rscons
 
     # Return whether this builder object is capable of producing a given target
     # file name from a given source file name.
+    #
     # @param target [String] The target file name.
     # @param source [String, Array] The source file name(s).
     # @param env [Environment] The Environment.
+    #
+    # @return [Boolean]
+    #   Whether this builder object is capable of producing a given target
+    #   file name from a given source file name.
     def produces?(target, source, env)
       false
     end
 
     # Check if the cache is up to date for the target and if not execute the
     # build command.
-    # Return the name of the target or false on failure.
+    #
+    # @param short_cmd_string [String]
+    #   Short description of build action to be printed when env.echo ==
+    #   :short.
+    # @param target [String] Name of the target file.
+    # @param command [Array<String>]
+    #   The command to execute to build the target.
+    # @param sources [Array<String>] Source file name(s).
+    # @param env [Environment] The Environment executing the builder.
+    # @param cache [Cache] The Cache object.
+    #
+    # @return [String,false]
+    #   The name of the target on success or false on failure.
     def standard_build(short_cmd_string, target, command, sources, env, cache)
       unless cache.up_to_date?(target, command, sources, env)
         cache.mkdir_p(File.dirname(target))
diff --git a/lib/rscons/builders/cfile.rb b/lib/rscons/builders/cfile.rb
index fe523cf..7534628 100644
--- a/lib/rscons/builders/cfile.rb
+++ b/lib/rscons/builders/cfile.rb
@@ -7,6 +7,11 @@ module Rscons
     #   env.CFile("parser.tab.cc", "parser.yy")
     #   env.CFile("lex.yy.cc", "parser.ll")
     class CFile < Builder
+      # Return default construction variables for the builder.
+      #
+      # @param env [Environment] The Environment using the builder.
+      #
+      # @return [Hash] Default construction variables for the builder.
       def default_variables(env)
         {
           "YACC" => "bison",
@@ -18,6 +23,16 @@ module Rscons
         }
       end
 
+      # Run the builder to produce a build target.
+      #
+      # @param target [String] Target file name.
+      # @param sources [Array<String>] Source file name(s).
+      # @param cache [Cache] The Cache object.
+      # @param env [Environment] The Environment executing the builder.
+      # @param vars [Hash,VarSet] Extra construction variables.
+      #
+      # @return [String,false]
+      #   Name of the target file on success or false on failure.
       def run(target, sources, cache, env, vars)
         vars = vars.merge({
           "_TARGET" => target,
diff --git a/lib/rscons/builders/disassemble.rb b/lib/rscons/builders/disassemble.rb
index 17a0d66..b5ba813 100644
--- a/lib/rscons/builders/disassemble.rb
+++ b/lib/rscons/builders/disassemble.rb
@@ -2,6 +2,11 @@ module Rscons
   module Builders
     # The Disassemble builder produces a disassembly listing of a source file.
     class Disassemble < Builder
+      # Return default construction variables for the builder.
+      #
+      # @param env [Environment] The Environment using the builder.
+      #
+      # @return [Hash] Default construction variables for the builder.
       def default_variables(env)
         {
           "OBJDUMP" => "objdump",
@@ -10,6 +15,16 @@ module Rscons
         }
       end
 
+      # Run the builder to produce a build target.
+      #
+      # @param target [String] Target file name.
+      # @param sources [Array<String>] Source file name(s).
+      # @param cache [Cache] The Cache object.
+      # @param env [Environment] The Environment executing the builder.
+      # @param vars [Hash,VarSet] Extra construction variables.
+      #
+      # @return [String,false]
+      #   Name of the target file on success or false on failure.
       def run(target, sources, cache, env, vars)
         vars = vars.merge("_SOURCES" => sources)
         command = env.build_command("${DISASM_CMD}", vars)
diff --git a/lib/rscons/builders/library.rb b/lib/rscons/builders/library.rb
index fc3cfdc..4545325 100644
--- a/lib/rscons/builders/library.rb
+++ b/lib/rscons/builders/library.rb
@@ -2,6 +2,11 @@ module Rscons
   module Builders
     # A default Rscons builder that produces a static library archive.
     class Library < Builder
+      # Return default construction variables for the builder.
+      #
+      # @param env [Environment] The Environment using the builder.
+      #
+      # @return [Hash] Default construction variables for the builder.
       def default_variables(env)
         {
           'AR' => 'ar',
@@ -11,6 +16,16 @@ module Rscons
         }
       end
 
+      # Run the builder to produce a build target.
+      #
+      # @param target [String] Target file name.
+      # @param sources [Array<String>] Source file name(s).
+      # @param cache [Cache] The Cache object.
+      # @param env [Environment] The Environment executing the builder.
+      # @param vars [Hash,VarSet] Extra construction variables.
+      #
+      # @return [String,false]
+      #   Name of the target file on success or false on failure.
       def run(target, sources, cache, env, vars)
         # build sources to linkable objects
         objects = env.build_sources(sources, env.expand_varref(["${OBJSUFFIX}", "${LIBSUFFIX}"], vars).flatten, cache, vars)
diff --git a/lib/rscons/builders/object.rb b/lib/rscons/builders/object.rb
index dd88758..848f284 100644
--- a/lib/rscons/builders/object.rb
+++ b/lib/rscons/builders/object.rb
@@ -3,6 +3,7 @@ module Rscons
     # A default Rscons builder which knows how to produce an object file from
     # various types of source files.
     class Object < Builder
+      # Mapping of known sources from which to build object files.
       KNOWN_SUFFIXES = {
         "AS" => "ASSUFFIX",
         "CC" => "CSUFFIX",
@@ -10,6 +11,11 @@ module Rscons
         "DC" => "DSUFFIX",
       }
 
+      # Return default construction variables for the builder.
+      #
+      # @param env [Environment] The Environment using the builder.
+      #
+      # @return [Hash] Default construction variables for the builder.
       def default_variables(env)
         {
           'OBJSUFFIX' => '.o',
@@ -51,12 +57,32 @@ module Rscons
         }
       end
 
+      # Return whether this builder object is capable of producing a given target
+      # file name from a given source file name.
+      #
+      # @param target [String] The target file name.
+      # @param source [String, Array] The source file name(s).
+      # @param env [Environment] The Environment.
+      #
+      # @return [Boolean]
+      #   Whether this builder object is capable of producing a given target
+      #   file name from a given source file name.
       def produces?(target, source, env)
         target.end_with?(*env['OBJSUFFIX']) and KNOWN_SUFFIXES.find do |compiler, suffix_var|
           source.end_with?(*env[suffix_var])
         end
       end
 
+      # Run the builder to produce a build target.
+      #
+      # @param target [String] Target file name.
+      # @param sources [Array<String>] Source file name(s).
+      # @param cache [Cache] The Cache object.
+      # @param env [Environment] The Environment executing the builder.
+      # @param vars [Hash,VarSet] Extra construction variables.
+      #
+      # @return [String,false]
+      #   Name of the target file on success or false on failure.
       def run(target, sources, cache, env, vars)
         vars = vars.merge({
           '_TARGET' => target,
diff --git a/lib/rscons/builders/preprocess.rb b/lib/rscons/builders/preprocess.rb
index ad35d55..39a4065 100644
--- a/lib/rscons/builders/preprocess.rb
+++ b/lib/rscons/builders/preprocess.rb
@@ -2,12 +2,27 @@ module Rscons
   module Builders
     # The Preprocess builder invokes the C preprocessor
     class Preprocess < Builder
+      # Return default construction variables for the builder.
+      #
+      # @param env [Environment] The Environment using the builder.
+      #
+      # @return [Hash] Default construction variables for the builder.
       def default_variables(env)
         {
           "CPP_CMD" => ["${_PREPROCESS_CC}", "-E", "-o", "${_TARGET}", "-I${CPPPATH}", "${CPPFLAGS}", "${CFLAGS}", "${_SOURCES}"],
         }
       end
 
+      # Run the builder to produce a build target.
+      #
+      # @param target [String] Target file name.
+      # @param sources [Array<String>] Source file name(s).
+      # @param cache [Cache] The Cache object.
+      # @param env [Environment] The Environment executing the builder.
+      # @param vars [Hash,VarSet] Extra construction variables.
+      #
+      # @return [String,false]
+      #   Name of the target file on success or false on failure.
       def run(target, sources, cache, env, vars)
         pp_cc = if sources.find {|s| s.end_with?(*env.expand_varref("${CXXSUFFIX}", vars))}
                   "${CXX}"
diff --git a/lib/rscons/builders/program.rb b/lib/rscons/builders/program.rb
index 89fab29..4785117 100644
--- a/lib/rscons/builders/program.rb
+++ b/lib/rscons/builders/program.rb
@@ -3,6 +3,11 @@ module Rscons
     # A default Rscons builder that knows how to link object files into an
     # executable program.
     class Program < Builder
+      # Return default construction variables for the builder.
+      #
+      # @param env [Environment] The Environment using the builder.
+      #
+      # @return [Hash] Default construction variables for the builder.
       def default_variables(env)
         {
           'OBJSUFFIX' => '.o',
@@ -18,6 +23,20 @@ module Rscons
         }
       end
 
+      # Create a BuildTarget object for this build target.
+      #
+      # The build target filename is given a ".exe" suffix if Rscons is
+      # executing on a Windows platform and no other suffix is given.
+      #
+      # @param options [Hash] Options to create the BuildTarget with.
+      # @option options [Environment] :env
+      #   The Environment.
+      # @option options [String] :target
+      #   The user-supplied target name.
+      # @option options [Array<String>] :sources
+      #   The user-supplied source file name(s).
+      #
+      # @return [BuildTarget]
       def create_build_target(options)
         my_options = options.dup
         unless my_options[:target] =~ /\./
@@ -26,6 +45,16 @@ module Rscons
         super(my_options)
       end
 
+      # Run the builder to produce a build target.
+      #
+      # @param target [String] Target file name.
+      # @param sources [Array<String>] Source file name(s).
+      # @param cache [Cache] The Cache object.
+      # @param env [Environment] The Environment executing the builder.
+      # @param vars [Hash,VarSet] Extra construction variables.
+      #
+      # @return [String,false]
+      #   Name of the target file on success or false on failure.
       def run(target, sources, cache, env, vars)
         # build sources to linkable objects
         objects = env.build_sources(sources, env.expand_varref(["${OBJSUFFIX}", "${LIBSUFFIX}"], vars).flatten, cache, vars)
diff --git a/lib/rscons/cache.rb b/lib/rscons/cache.rb
index 28dcfa8..6079010 100644
--- a/lib/rscons/cache.rb
+++ b/lib/rscons/cache.rb
@@ -84,7 +84,8 @@ module Rscons
       @dirty = false
     end
 
-    # Check if target(s) are up to date
+    # Check if target(s) are up to date.
+    #
     # @param targets [String, Array] The name(s) of the target file(s).
     # @param command [String, Array] The command used to build the target.
     # @param deps [Array] List of the target's dependency files.
@@ -93,6 +94,7 @@ module Rscons
     # @option options [Boolean] :strict_deps
     #   Only consider a target up to date if its list of dependencies is
     #   exactly equal (including order) to the cached list of dependencies
+    #
     # @return [Boolean]
     #   True value if the targets are all up to date, meaning that,
     #   for each target:
@@ -144,11 +146,14 @@ module Rscons
       true
     end
 
-    # Store cache information about target(s) built by a builder
+    # Store cache information about target(s) built by a builder.
+    #
     # @param targets [String, Array] The name of the target(s) built.
     # @param command [String, Array] The command used to build the target.
     # @param deps [Array] List of dependencies for the target.
     # @param env [Environment] The {Rscons::Environment}.
+    #
+    # @return [void]
     def register_build(targets, command, deps, env)
       Array(targets).each do |target|
         @cache["targets"][target] = {
@@ -171,13 +176,19 @@ module Rscons
       end
     end
 
-    # Return a list of targets that have been built
+    # Return a list of targets that have been built.
+    #
+    # @return [Array<String>] List of targets that have been built.
     def targets
       @cache["targets"].keys
     end
 
     # Make any needed directories and record the ones that are created for
     # removal upon a "clean" operation.
+    #
+    # @param path [String] Directory to create.
+    #
+    # @return [void]
     def mkdir_p(path)
       parts = path.split(/[\\\/]/)
       parts.each_index do |i|
@@ -191,7 +202,10 @@ module Rscons
       end
     end
 
-    # Return a list of directories which were created as a part of the build
+    # Return a list of directories which were created as a part of the build.
+    #
+    # @return [Array<String>]
+    #   List of directories which were created as a part of the build.
     def directories
       @cache["directories"].keys
     end
@@ -213,14 +227,20 @@ module Rscons
     end
 
     # Return a file's checksum, or the previously calculated checksum for
-    # the same file
+    # the same file.
+    #
     # @param file [String] The file name.
+    #
+    # @return [String] The file's checksum.
     def lookup_checksum(file)
       @lookup_checksums[file] || calculate_checksum(file)
     end
 
-    # Calculate and return a file's checksum
+    # Calculate and return a file's checksum.
+    #
     # @param file [String] The file name.
+    #
+    # @return [String] The file's checksum.
     def calculate_checksum(file)
       @lookup_checksums[file] = Digest::MD5.hexdigest(File.read(file, mode: "rb")) rescue ""
     end
diff --git a/lib/rscons/environment.rb b/lib/rscons/environment.rb
index 9e40dc1..085095d 100644
--- a/lib/rscons/environment.rb
+++ b/lib/rscons/environment.rb
@@ -7,25 +7,33 @@ module Rscons
   # contains a collection of construction variables, options, builders, and
   # rules for building targets.
   class Environment
-    # Hash of +{"builder_name" => builder_object}+ pairs.
+    # @return [Hash] Set of \{"builder_name" => builder_object} pairs.
     attr_reader :builders
 
     # :command, :short, or :off
     attr_accessor :echo
 
-    # String or +nil+
+    # @return [String, nil] The build root.
     attr_reader :build_root
+
+    # Set the build root.
+    #
+    # @param build_root [String] The build root.
     def build_root=(build_root)
       @build_root = build_root
       @build_root.gsub!('\\', '/') if @build_root
     end
 
     # Create an Environment object.
+    #
     # @param options [Hash]
-    # Possible options keys:
-    #   :echo => :command, :short, or :off (default :short)
-    #   :build_root => String specifying build root directory (default nil)
-    #   :exclude_builders => true to omit adding default builders (default false)
+    # @option options [Symbol] :echo
+    #   :command, :short, or :off (default :short)
+    # @option options [String] :build_root
+    #   Build root directory (default nil)
+    # @option options [Boolean] :exclude_builders
+    #   Whether to omit adding default builders (default false)
+    #
     # If a block is given, the Environment object is yielded to the block and
     # when the block returns, the {#process} method is automatically called.
     def initialize(options = {})
@@ -108,6 +116,10 @@ module Rscons
     end
 
     # Add a {Builder} object to the Environment.
+    #
+    # @param builder [Builder] The {Builder} object to add.
+    #
+    # @return [void]
     def add_builder(builder)
       @builders[builder.name] = builder
       var_defs = builder.default_variables(self)
@@ -119,19 +131,45 @@ module Rscons
     end
 
     # Add a build hook to the Environment.
+    #
+    # @yield [build_op]
+    #   Invoke the given block with the current build operation.
+    # @yieldparam build_op [Hash]
+    #   Hash with keys:
+    #   - :builder - The builder object in use.
+    #   - :target - Target file name.
+    #   - :sources - List of source file(s).
+    #   - :vars - Set of construction variable values in use.
+    #   - :env - The Environment invoking the builder.
+    #
+    # @return [void]
     def add_build_hook(&block)
       @build_hooks << block
     end
 
     # Specify a build directory for this Environment.
+    #
     # Source files from src_dir will produce object files under obj_dir.
+    #
+    # @param src_dir [String] Path to the source directory.
+    # @param obj_dir [String] Path to the object directory.
+    #
+    # @return [void]
     def build_dir(src_dir, obj_dir)
       src_dir = src_dir.gsub('\\', '/') if src_dir.is_a?(String)
       @build_dirs << [src_dir, obj_dir]
     end
 
-    # Return the file name to be built from source_fname with suffix suffix.
+    # Return the file name to be built from +source_fname+ with suffix
+    # +suffix+.
+    #
     # This method takes into account the Environment's build directories.
+    #
+    # @param source_fname [String] Source file name.
+    # @param suffix [String] Suffix, including "." if desired.
+    #
+    # @return [String]
+    #   The file name to be built from +source_fname+ with suffix +suffix+.
     def get_build_fname(source_fname, suffix)
       build_fname = Rscons.set_suffix(source_fname, suffix).gsub('\\', '/')
       found_match = @build_dirs.find do |src_dir, obj_dir|
@@ -151,26 +189,32 @@ module Rscons
     end
 
     # Access a construction variable or environment option.
+    #
     # @see VarSet#[]
     def [](*args)
       @varset.send(:[], *args)
     end
 
     # Set a construction variable or environment option.
+    #
     # @see VarSet#[]=
     def []=(*args)
       @varset.send(:[]=, *args)
     end
 
     # Add a set of construction variables or environment options.
+    #
     # @see VarSet#append
     def append(*args)
       @varset.append(*args)
     end
 
-    # Build all target specified in the Environment.
+    # Build all build targets specified in the Environment.
+    #
     # When a block is passed to Environment.new, this method is automatically
     # called after the block returns.
+    #
+    # @return [void]
     def process
       unless @targets.empty?
         expand_paths!
@@ -227,13 +271,16 @@ module Rscons
     end
     alias_method :build_command, :expand_varref
 
-    # Execute a builder command
+    # Execute a builder command.
+    #
     # @param short_desc [String] Message to print if the Environment's echo
     #   mode is set to :short
     # @param command [Array] The command to execute.
     # @param options [Hash] Optional options, possible keys:
     #   - :env - environment Hash to pass to Kernel#system.
     #   - :options - options Hash to pass to Kernel#system.
+    #
+    # @return [true,false,nil] Return value from Kernel.system().
     def execute(short_desc, command, options = {})
       print_command = proc do
         puts command.map { |c| c =~ /\s/ ? "'#{c}'" : c }.join(' ')
@@ -253,6 +300,14 @@ module Rscons
       end
     end
 
+    # Define a build target.
+    #
+    # @param method [Symbol] Method name.
+    # @param args [Array] Method arguments.
+    #
+    # @return [BuildTarget]
+    #   The {BuildTarget} object registered, if the method called is a
+    #   {Builder}.
     def method_missing(method, *args)
       if @builders.has_key?(method.to_s)
         target, sources, vars, *rest = args
@@ -269,6 +324,15 @@ module Rscons
       end
     end
 
+    # Add a build target.
+    #
+    # @param target [String] Build target file name.
+    # @param builder [Builder] The {Builder} to use to build the target.
+    # @param sources [Array<String>] Source file name(s).
+    # @param vars [Hash] Construction variable overrides.
+    # @param args [Object] Any extra arguments passed to the {Builder}.
+    #
+    # @return [void]
     def add_target(target, builder, sources, vars, args)
       @targets[target] = {
         builder: builder,
@@ -290,20 +354,28 @@ module Rscons
       @user_deps[target] = (@user_deps[target] + user_deps).uniq
     end
 
-    # Return the list of user dependencies for a given target, or +nil+ for
-    # none.
+    # Return the list of user dependencies for a given target.
+    #
+    # @param target [String] Target file name.
+    #
+    # @return [Array<String>,nil]
+    #   List of user-specified dependencies for the target, or nil if none were
+    #   specified.
     def get_user_deps(target)
       @user_deps[target]
     end
 
     # Build a list of source files into files containing one of the suffixes
     # given by suffixes.
+    #
     # This method is used internally by Rscons builders.
+    #
     # @param sources [Array] List of source files to build.
     # @param suffixes [Array] List of suffixes to try to convert source files into.
     # @param cache [Cache] The Cache.
     # @param vars [Hash] Extra variables to pass to the builder.
-    # Return a list of the converted file names.
+    #
+    # @return [Array<String>] List of the converted file name(s).
     def build_sources(sources, suffixes, cache, vars)
       sources.map do |source|
         if source.end_with?(*suffixes)
@@ -325,12 +397,14 @@ module Rscons
     end
 
     # Invoke a builder to build the given target based on the given sources.
+    #
     # @param builder [Builder] The Builder to use.
     # @param target [String] The target output file.
     # @param sources [Array] List of source files.
     # @param cache [Cache] The Cache.
     # @param vars [Hash] Extra variables to pass to the builder.
-    # Return the result of the builder's run() method.
+    #
+    # @return [String,false] Return value from the {Builder}'s +run+ method.
     def run_builder(builder, target, sources, cache, vars)
       vars = @varset.merge(vars)
       @build_hooks.each do |build_hook_block|
@@ -516,6 +590,8 @@ module Rscons
     # This method expand construction variable references in the target and
     # source file names before passing them to the builder. It also expands
     # "^/" prefixes to the Environment's build root if a build root is defined.
+    #
+    # @return [void]
     def expand_paths!
       @targets = @targets.reduce({}) do |result, (target, target_params)|
         sources = target_params[:sources].map do |source|
@@ -530,9 +606,13 @@ module Rscons
     end
 
     # Parse dependencies for a given target from a Makefile.
+    #
     # This method is used internally by Rscons builders.
+    #
     # @param mf_fname [String] File name of the Makefile to read.
     # @param target [String] Name of the target to gather dependencies for.
+    #
+    # @return [Array<String>] Paths of dependency files.
     def self.parse_makefile_deps(mf_fname, target)
       deps = []
       buildup = ''
diff --git a/lib/rscons/varset.rb b/lib/rscons/varset.rb
index 2c53237..be575d8 100644
--- a/lib/rscons/varset.rb
+++ b/lib/rscons/varset.rb
@@ -1,9 +1,9 @@
 module Rscons
-  # This class represents a collection of variables which can be accessed
-  # as certain types.
-  # Only nil, strings, arrays, and hashes should be stored in a VarSet.
+  # This class represents a collection of variables which supports efficient
+  # deep cloning.
   class VarSet
     # Create a VarSet.
+    #
     # @param vars [Hash] Optional initial variables.
     def initialize(vars = {})
       @my_vars = {}
@@ -11,8 +11,10 @@ module Rscons
       append(vars)
     end
 
-    # Access the value of variable as a particular type
+    # Access the value of variable.
+    #
     # @param key [String, Symbol] The variable name.
+    #
     # @return [Object] The variable's value.
     def [](key)
       if @my_vars.include?(key)
@@ -29,15 +31,19 @@ module Rscons
     end
 
     # Assign a value to a variable.
+    #
     # @param key [String, Symbol] The variable name.
+    #
     # @param val [Object] The value to set.
     def []=(key, val)
       @my_vars[key] = val
     end
 
     # Check if the VarSet contains a variable.
+    #
     # @param key [String, Symbol] The variable name.
-    # @return [true, false] Whether the VarSet contains a variable.
+    #
+    # @return [Boolean] Whether the VarSet contains the variable.
     def include?(key)
       if @my_vars.include?(key)
         true
@@ -48,8 +54,11 @@ module Rscons
       end
     end
 
-    # Add or overwrite a set of variables
+    # Add or overwrite a set of variables.
+    #
     # @param values [VarSet, Hash] New set of variables.
+    #
+    # @return [self]
     def append(values)
       coa!
       if values.is_a?(VarSet)
@@ -62,7 +71,10 @@ module Rscons
     end
 
     # Create a new VarSet object based on the first merged with other.
+    #
     # @param other [VarSet, Hash] Other variables to add or overwrite.
+    #
+    # @return [VarSet] The newly created VarSet.
     def merge(other = {})
       coa!
       varset = self.class.new
@@ -71,9 +83,13 @@ module Rscons
     end
     alias_method :clone, :merge
 
-    # Replace "$" variable references in varref with the variables values,
-    # recursively.
+    # Replace "$\{var}" variable references in varref with the expanded
+    # variables' values, recursively.
+    #
     # @param varref [String, Array] Value containing references to variables.
+    #
+    # @return [String, Array]
+    #   Expanded value with "$\{var}" variable references replaced.
     def expand_varref(varref)
       if varref.is_a?(Array)
         varref.map do |ent|
@@ -99,6 +115,8 @@ module Rscons
     private
 
     # Move all VarSet variables into the copy-on-access list.
+    #
+    # @return [void]
     def coa!
       unless @my_vars.empty?
         @coa_vars.unshift(@my_vars)
@@ -107,8 +125,13 @@ module Rscons
     end
 
     # Create a deep copy of an object.
-    # @param obj [nil, String, Array, Hash] Object to deep copy.
-    # @return [nil, String, Array, Hash] Deep copied value.
+    #
+    # Only objects which are of type String, Array, or Hash are deep copied.
+    # Any other object just has its referenced copied.
+    #
+    # @param obj [Object] Object to deep copy.
+    #
+    # @return [Object] Deep copied value.
     def deep_dup(obj)
       obj_class = obj.class
       if obj_class == Hash