Some warnings before you buy this book
I bought this book a couple of weeks ago (May 2009) as an experienced developer trying to learn the RoR world. The title, "Beginning Ruby on Rails" and my initial scan of the book in the store indicated it was a good fit from an experienced author on a good publisher.
First the pros - the book itself is very clear in it's instructions and obviously was well proof-read at the time it was written, which was good for 2007.
Now the warning - the book is based on an older version of Rails which is no longer available. By chapter 5 you start to notice that certain pieces of code don't work resulting in extensive Google searches for the right values and code snippets. Obviously this forum also explains how some of these changes should be made. Unfortunately if I have to scan the web and read forums to tell me how to get the code working, it kinda defeats the purpose of buying the book in the first place.
You will learn a lot from the book and also a lot from scanning all the various websites looking for updated code and translating from Rails 1.8 to Rails 2.0 but the current version of this book certainly won't work standalone. Don't take it on a plane with you :)