I read this book as someone who has years of programming experience (Python, mostly) and wanted to have a grasp on the Ruby language.
Well, if you already have experience in programming, you probably already are aware of most of the concepts that are in this book and you won’t get much of new knowledge on it.
What looked like for me is that the title is a little misleading. I expected a more thorough explanation of Ruby features and caveats, and what I got was what looks like a good book for a beginner in programming, but a really slow book for somebody who already is into programming.