This is the worst R book you could imagine, especially after considering the fact it is actually accompanying an online course. So, simply, the book doesn't add anything to the course, which by the way, is a very bad-instructed and terrible course. It is not clear who the audience is, since the chapters are not in the same level. For instance, from very basic packages and tools, it jumps to very narrow topic of how to use multi-cores to speed up the calculations!
I think if you want to benefit the most from the whole material provided in this course, simply install the swirl package, which is a complementary source for practicing what you are supposed to learn during the course, or read in the book. I think it is worth using that if you are a beginner, and then you've exploited the whole course!