There are concrete tips on how to act. For example, an actor doesn't need to bring up things that are already in the script while acting. For instance, if in the script a person has lost their job, the actor doesn't need to act out "losing their job." The audience hears that the character has lost their job, sees the actor performing on stage and thinks "oh, that's how it looks." The actor only needs to focus on the question "what would I do" - that is, on the action, not on the internal states. The magic of the theater takes care of the rest.
Given that Mamet's main point is that acting cannot be learned, and there isn't really much theory related to it. There is a lot of yapping and repetition that could have been left out.
Interesting. It seems that he has written this mainly as a counter to Stanislavsky’s teachings. However, the work he advocates for is actually how most of the (admittedly excellent) acting teachers I have had have presented his work. Just like in voice teaching, everyone gets very worked up about one technique or another and doesn't slow down long enough to realize that they are all advocating for exactly the same thing and nearly identical ways of achieving it.
The volume is thinner, though. And although it may be a bit pretentious, it is happily direct and surprisingly empowering once you get past the abrasiveness of the first few chapters. It offers a unique perspective on acting and challenges the traditional ways of thinking about it. It makes you question the established norms and consider new approaches. Overall, it is an interesting read that can provide valuable insights for actors and acting teachers alike.