Really well laid out book, only problem is it's a bit outdated. They outline how to build apps using rails version 2 in the book, whereas the current version is rails 3! You'll come across several sections where you'll need to find answers to problems not mentioned in the book if you use rails 3, with simply rails 2.
If you want, there is a book which will teach how to use rails 3. No opinion on it myself, as I haven't read it, but I've *heard* it's pretty good.