Ruby Book List
You're taking your first steps into Ruby
A good introduction to programming in general. Easy on newer programmers.
A good introduction to Ruby and its' style. Slightly more in depth than the Well Grounded Rubyist as far as language tricks.
The pickaxe book, written by some of the best in the industry and often mentioned as the de-facto starting point
An illustrated guide to Ruby written by yours truly. Currently a work in progress, but aims to teach Ruby to complete beginners using pictures of Lemurs and various programming concepts.
You've got the basics, now it's time to refine them a bit and get your references
Practical Object Oriented Design in Ruby covers how OO should work in Ruby and helps you on your way to leveraging that power.
The GoF book comes to Ruby. Be forewarned that you should read POODR first and take some of these patterns with a heavy grain of salt.
Learn how to write Ruby confidently, avoiding patch hacks and ugly kludgery.
Making code work is one thing, making it behave itself with failure? Learn about Ruby exceptions and their power.
Doing things with Ruby
So you've learned Ruby, now what?
Get a feel for some more practical Ruby usage
Using the advanced features of the language or just outright difficult concepts.
Want to learn some black magic in Ruby? All of that meta-goodness that you've heard about explained in depth.
Learn the foundations of Computer Science in Ruby.
Take a look at what makes Ruby tick, all the way down to its' compilation.
If you thought that Metaprogramming Ruby was trippy, stay away. This book covers functional combinators in depth in Ruby and gives you a view of what lambdas can really do. Not for the faint of heart, this book has some incredible ideas and writing.
One of the most popular testing frameworks in Ruby
The traditional standard in RSPEC, and for good reason.
Written by one of the writers of RSpec and probably the best book on testing out on the market currently.
Minitest is a lightweight alternative to RSpec
A detailed guide on getting started with and using Minitest effectively