to be honest, this is a just ok book. For ROR beginners, stick with Micheal's tutorial. http://ruby.railstutorial.org/
Git repositories, test driven development, etc are all things a beginner doesn't care about and doesn't really need to know about when starting out.
I can't think of anyone I've taught git to who didnt see how powerful and easy it makes life.
It introduces way too much for a pure beginner who knows little-to-no programming trying to get started. That said, I really don't think someone brand new to coding should learn RoR straight away.