I did the Reinforcement learning specialization on Coursera (https://www.coursera.org/specializations/reinforcement-learn...), which used this book. The specialization was great, but I would say that I had a lot of trouble following this book. I would find that there was a concept I didn't quite get, and then other things would build on top of that concept. I ended up feeling like I didn't quite grasp everything, even though I read most of the chapters more than once.

I do feel like there are a lot of things that aren't fully explained in this book, and maybe it is expected that the reader has some prior knowledge that I didn't have. For example, they never really explain the basic notation for backup diagrams. They just show one and mention that they are a thing. The mathematical notation they use also isn't really explained - they just start showing formulas of increasing complexity. It's possible to look these things up elsewhere, but they probably could have spent just a little bit more time explaining some of the basics and made it easier to follow.