This is a great introductory book. It's really the only "traditional" book I am recommending at this stage in the game. It's a bit old, but it's free to read online.
Try Ruby is an interactive tour of Ruby. It gives you a command prompt like the one we were fucking around with yesterday and takes your through some of the basic functionality of Ruby. It takes about 20 minutes and it's totally worth it. Don't worry about remembering everything and feel free to do it again in a few weeks.
Instead of trying to make learning to program fun, Zed Shaw focuses on just having you type commands over and over until you get an understanding of what they do and how everything works. This technique is surprisingly effective, actually.
Michael Hartl's book on Ruby on Rails will take you all the way from basic Ruby knowledge to being able to deploy a real deal web application. If you can get through this book, you can probably call yourself a web developer. Not only does he cover how to use Rails, he covers a ton of best practice stuff. It's an incredible book.
Why's (Poignant) Guide to Ruby
Alright, I'll warn you up front: this book is trippy. For extra credit, you can read the mystery surrounding the author, Why the Lucky Stiff.
Dan is a journalist and he uses Ruby to get his job done. This book is about practical uses of Ruby above everything else. You'll learn how to scrap information from web sites, automating repetitive web tasks, batch editing images, and processing tons of data.