Expired. That's the most appropriate word I can think of for this book. Brad Ediger does a fine job explaining advanced concepts in Rails, however, this book is from 2007 and lots of things have changed in seven years. I'm not even a big time Ruby guy and I was able to spot various points where I knew that the Rails community had evolved to some other technology.
I don't think I can recommend this book because it is laced thoroughly with all sorts of plugins and tools. Without doing a bunch of research of all these tools, there is no way to know how many are still valid today.
The book contained plenty of general advice for dealing with Rail, but I don't think it is worth digging through all the nitty gritty details to find it.
Easily the best Rails book I have read in the past six months. It provides great insight into may of the issue that experienced Rails programmers are presented with. This book is a nice supplement to my Rails bookshelf.