I've been working through The Rails Way by Obie Fernandez and it is most definitely the best reference text for Rails I've come across so far. It's in depth, informative and even opinionated in places.
It covers Rails 2.0 but I found that throughout the text there were strange omissions - no mention of Sexy Migrations for example even though they've been there for nine months now. Having said that keeping up with a fast moving target like Rails can't be easy when you have a hungry publisher breathing down your neck.
Anyway if you're a Rails developer you need this book.