Programming Ruby 1.9: The Pragmatic Programmer's Guide Book

This enormous book covers most of what you want to know about Ruby, and everything you never wanted to know. Its overview of the language is decent but seems poorly organized. It jumps back-and-forth between basic and advanced. Beginners would feel lost, while more advanced programmers have to skip around carefully. But if you don't skip around too much, you'll find nuggets that explain things much better than any other Ruby book. It also covers tangential subjects that you won't find in most Ruby books--RDoc, RSpec, Shoulda, IRB, and writing C extensions. The best part of this book is the reference manual at the end. It's more thorough and organized than any other Ruby book I've seen.