DHH wrote it.
Obviously Agile Web Development with Rails is the bible of RoR books: http://www.pragmaticprogrammer.com/titles/rails2/
I'd personally be wary of many of the RoR tutorials you'll find online: none of the ones I used did a good job of explaining rails at the conceptual level: you'll end up with a rails app from the tutorial, but limited understanding of what you did and why.
Updated:
This page has a good selection of relevant books: http://www.sapphiresteel.com/Ruby-and-Rails-Books-the-essential
My opinion is that one should begin with a Rails-specific book or tutorial and not feel the need to learn Ruby first. Much of rails code is specific to rails and, while you'll want to master Ruby eventually, you'll get enough from the Rails books.
List of 12 very good tutorials.
Rolling On Rails from OnLamp is a very quick and useful tutorial found here: http://www.onlamp.com/pub/a/onlamp/2005/01/20/rails.html
This is the easiest and fastest way to get started: http://tryruby.hobix.com/
http://www.onlamp.com/pub/a/onlamp/2006/12/14/revisiting-ruby-on-rails-revisited.html
It's nearly 2 years more recent and up-to-date with Rails changes.