Replicating tutorials as books seems a growing trend, and the economic motivations are still a enigma for me. As the writer of a few technical books myself, arguing over original content has always been a constant battle with editors and publishers.
Without any intention of stealing protagonismo and a surely dedicated effort from the author, the book is a compilation from the Git technical documentation not even meticulously. The chapter of Continuous Integration might drop some extra light on branching techniques and real world examples, but only as a colateral effect happening after explaining Git and nothing that more specialized literature has not covered.
If you are new to Git and have absolutely no idea what it is, then this book is for you. It covers everything from installing, configuring and starting to work with it to such things as hooks, CI and flow. Yet I can't really say what would be more of help - reading this or the official Git documentation. Also, it is assumed here that you know some Linux commands, such as how to create, rename, delete files/directories and so on. So Win and Mac users might find yourself a little frustrated here.
But if you already know Git and want to read this book for Best practicies as the name suggests... Well, you can skip right to the last two chapters. There you will find some interesting stuff about workflow, branching system, CI, etc. But it won't be enough, to be honest. It just encourages you to go find more information about it somewhere else.
So, it's a good book for complete beginners, but it shouldn't be named "Git Best Practices" as it is just basics plus some of the advanced techinques.