I've read the 1st edition and now the 3rd edition. Still seems like the best book for a rails newbie. My nitpick: this book doesn't have a concise roadmap to what's new in Rails 3.
Essential reading for savvy designers and developers cleverly boarding the ruby on rails train. All designers should learn to code. Ruby is a beautiful language and rails makes a practical partner to bring your next napkin sketch into reality. This book was written in part by DHH, the creator of rails among other things. That rendered the book a trusted source for conventions and best practices.
The intro says that you can keep up if you don't know ruby and with relatively little CSS/HTML but I don't think so. I don't know much about CSS or HTML but I know ruby and have written two applications using Sinatra and MVC. Everything seems easy, I am trying to cope with the abstraction level but I wouldn't say that this book is for beginners. On the other hand I like its approach, goes directly to web development without loosing too much over various subjects, rails is a framework after all, nothing more.
I did not finish this... It is a great reading for the first chapters but the technology advancements on this topic are too fast for my reading pace! Waiting to get a copy for the Rails 3 version!