If anything, you might be a bit lost at times if you ask too many  
questions in the first chapter or 2 of Ruby for Rails. When he says a  
breadth first approach, he means it. You create a simple rails app  
right away, and you don't get much explanation, so if you start to  
tinker you will wonder why things are kind of incomplete. They are.  
It is an attempt to take you through the overall process all at once.
Then he breaks it down a bit more. Explaining some things, like how  
somethings in Rails are the way they are because of how Ruby can do  
things. That's true. As you get going though, you will want and  
should stop and get the Pickaxe book. It really is indispensible. The  
only bad thing is that it is not sold as a two volume set rather than  
as one behemoth monster that is half reference and half tutorial. It  
would be much easier to keep the reference half at home and take the  
other with you or vice-versa. (pragmatic does sell pdf versions of  
its books though!)