Ruby Cookbook from O'Reilly

Ruby Cookbook: Recipes for Object-Oriented Scripting
by Lucas Carlson & Leonard Richardson

ISBN 0-596-52369-6

I haven't read this book cover-to-cover, but I have given it a very thorough inspection, skimming through sections to find points of interest and then stopping to read those recipes. So, actually, I've probably read a whole bunch of the book and didn't realize it.

The book is written in a very concise manner, with plenty of examples, lots of useful code, excellent cross-references and a very generous license that allows you to use the code from the book (albeit with some restrictions).

Each recipe is presented as a quartet of Problem, Solution, Discussion and See Also sections. Each problem is presented succinctly, and the solutions dive right into the required code (with code comments explaining some of the more complicated lines of code, but not explaining the self-documenting lines). The discussion section of each solution really digs into what is going on, code choices that were made, variations, and basically anything else that might be interesting. The see also section cross-references other recipes that may be pertinent to the given problem.

All told, this book does an amazing job of going through a wide range of problems, from Strings & Numbers to Meta-Programming & Rails and Graphics. This book is loaded with useful bits of information and I would highly recommend adding it to your collection.