This enormous book provides tons of ready-made Ruby code snippets for common and not-so-common problems. With books this big, I usually suspect the author of wasting words, but not this one. It just covers a ton of stuff, everything I could fathom anyone would want to use the language for, including object-oriented programming, metaprogramming, MIDI, XML, HTML, graphics, databases, persistence, internet services, web development (Ruby on Rails), web services, distributed programming, debugging, testing, optimizing, testing, packaging, automation, multitasking, multithreading, GUI, command line interfaces, C extensions, and system administration. Like I said, EVERYTHING.
Each solution also comes with a thorough discussion, which really helps you understand the solution in-depth. These "recipes" aren't intended to document everything completely, but to give you a good understanding of it, and tell you where to look for more information. They're like mini-tutorials. Plus, this book also provides fun little tricks that aren't necessarily useful, but really interesting. These are like dessert recipes.
The best part is, most everything in this book is well-written and easy to follow. Things I thought I'd already understood, this book helped me understand better, and it really got me a lot more comfortable reading Ruby code. The book is also arranged in a very logical way. I think this is the perfect reference manual, not only for syntax, but also for how to solve problems. And yet, despite its enormous size and excellence as a reference, it's also surprisingly easy to just read cover-to-cover.