The book itself is broken down into 12 different sections, each focused on a different tactic like Pins, Knight Forks, Skewers, etc. Each one is a series of exercises to solve, with a total of over 400 exercises.
I actually worked through this book a few times and ended up buying two copies of the book. The first time through I wrote down all the answers in the book. Then I wanted to go through again but I couldn’t stop looking at the answers so I bought a second blank copy. I made myself a worksheet that had all the blank moves to fill in, so I could write down the answers multiple times.
I also found most of the tactics as Lichess studies. After going through the book a couple of times I started reviewing these studies online. You can search for them, but you should buy the book first! Also, the studies I found were not always accurate. I wanted to make my own versions of the studies, but that would be a lot of work.
Lichess puzzles do have themes that roughly relate to some of the sections in the books. These might be good training:
It is hard to say how much this helped. I did continue my climb in rapid rating, gaining 150 points to 1200 while I was working through this book. I’d like to think this was because of this book, but I was also playing more and analyzing games so it was likely a combination of those things.
For me, I found it easy to do a set of these exercises when I knew what to look for. For example, when I was looking at the section on Discovered Checks, I was usually able to find the tactic pretty easily. I need to work on finding those tactics when I am not specifically looking for a certain tactic.