Just a bit of background, i'm primarily a recreational player who finds playing poker or studying poker very interesting.
Having said that, i probably study a lot more about poker than i play. I've studied quite a number of poker courses, RYE Tournament Masterclass, From The Ground Up Cash and MTT, Bluff the Spot etc etc, as well as quite a few poker books, Harrington, etc etc
Make no mistake, the courses above provide a lot of value, as for the poker books, they are just abit outdated.
However, when it came to this book, in terms of time spent, there is nothing better better/more efficient.
The author uses solvers/icmizers to derive first principles, he clearly explains the first principles and its logic, how icm affects the game at different stages, and provide the essential examples.
For most poker players, who do not intend to go professional, or spend more than 12 hours a day playing/studying poker, this is probably the most important thing.
And for professionals, the first principles he provided will cover 80% of all you need to know (which should reduce big leaks and turn you from a big losing player, to a marginally losing / break-even / profitable player depending on stakes, and how well you apply the content), and provide you a clear path to study the remaining 20% needed to crush the games.
And all this for 10 dollars, most poker courses charge easily more than 500-1k dollars.