An outstanding book which richly deserves five stars, despite some dreadful presentation, which you can fix yourself by annotating the diagrams.
The back cover says that the club players the author was coaching had great weaknesses in the tactical play, which were not fixed solving a huge number of puzzles. Inside the book, he says that with his coaching the players improved by an average of 100-200 rating points and promoted to higher leagues twice in three years, using the forerunner of the material in the book. Clearly, this was not a scientific test of his methods, and the improvement programme was not a short term endeavour. Nonetheless, the book has a good motivational story - and is a good read as well - so full points for motivation.
The main theme of the book is how to find clues for tactics by studying the characteristics of the position, before you start to analyse moves. The book makes a much better job of this than any other I have seen - and clearly this is very important - you will waste a lot of time if you start analysing before you have taken the trouble to understand the position properly! In addition, you will not learn very effectively, if you do not fully understand what made the tactics work.
So what is the presentational problem? None of the diagrams say who it is to move! You often have to read quite a long way through the text to find out, and by doing so be told the solution, before you have even had a chance to look at the position! Very annoying. In addition, a fair proportion of the diagrams are not really puzzle positions - in some cases a mistake has to be made before the puzzle position arises - or the example is a speculative Tal sacrifice, which does not actually win against the (very hard to find) best defence. Furthermore, it is very clear from the text that the author expects that you have been studying the positions, before being told the answers. All the diagrams need an indicator to say whose move it is, and a caption to tell us whether we can profitably study them before reading on. Fortunately, you can add this information yourself with a couple of hours work.
As others have said, there are only four exercises per chapter, but if you annotate the book as I suggest, the main text provides many more per chapter. You can apply what you have learned in this book to the positions in puzzle books. Nonetheless, like in a maths exam, it is important not only that you find the right answer, but that you find it in the right way, so the author's solutions are more helpful than you usually find in most puzzle books. Perhaps there is an opportunity for a follow up book here?
Despite the problems, this is still a five star book. What really matters is how effective the book is likely to be in improving your chess. A few hours annotating the book is a relatively small overhead, compared with the work necessary to fully digest the contents of this book, and fully incorporate the ideas into the habitual (and largely automatic) thought processes that you use when sitting at the board. This book really can improve you chess - if you work hard enough at it!