This book will not be particularly helpful to inexperienced players of the game. For these players, I think time will be much better spent getting a grasp of basic strategy. If you don't understand basic strategy, you will never understand how to use these tells correctly. At the end of the day, if you're in position on the flop with JJ on 10 9 4 rainbow, you should c-bet regardless of the tell you read from your opponent. I think the use case of this book is mostly in higher level games, where people are not leaking through unsound, exploitable strategies and are approximating game theory optimal play. At these higher levels, there are diminishing returns to getting theoretically better at the game such that huge gains can be made by picking up small tells in big spots.
While the book started off strong, I was annoyed by how poorly organized this book was. Rather than beginning with first principles and then systematically discussing specific tells, the book is organized in a series of increasingly redundant chapters. After the first 100 pages, maybe 70% of the book is repetitive. That said, I'm excited to employ some of Navarro's tips next time I play live poker.