I am learning Ruby programming, for starters. The advantages of this book include:

1. up-to-date (covers Ruby 1.8 instead of older versions)
2. in-depth description of the language
3. instructions on how to do testing
4. description of the Ruby runtime environment
5. comprehensive Library documentation for built-in and core classes
6. clear, easy-to-understand writing
7. good organization
8. very nice, handy table of contents and index

The book introduces the reader to the Ruby programming language and the tools that come with it in the first half. The second half documents the standard Ruby library.

No one book can cover everything, and do it well. So there are some things this book does not cover. Mostly, third-party add-on libraries, frameworks, and tools.

For instance, although Ruby on Rails frame and Rake tool are mentioned, they are not extensively covered.

If you plan to use Rails, you will want to get a book that describes that as well. I have the one from the Pragmatic Programmer series for that as well, and it is of the same high quality as this book. This one makes a good compliment for that one – since the Rails book assumes you already know Ruby.