While the first chapters are a refreshing take on Rails and easy to understand the book is getting kind of cloudy later when covering more complex topics. Cumbersome explanations followed by wack examples give you a hard time—you cannot easily grasp basic ideas, so you constantly switch between examples and theory but you just don't get it.
Especially, chapter 13 (on Singleton methods) is miserable. Admitting Ruby's Singleton Pattern isn't the easiest thing the book totally failed from here: I read this chapter dozen times until I gave up and just googled better explanations and I am sorry to say that every blog post about the Singleton Pattern did a far, far better job than this book. And from this point I did it with all following chapters—just scanned them briefly and googled better articles for respective subjects. This book was definitely not worth the money but at least I did again some Rails theory with the book as guideline.