Disclaimer: I only read up to (and including) chapter 7, even though I learned the contents of the book through my university module that included the material, except chapter 10 and 11. The HUGE appendix, I just dipped into a bit, without studying/making use of it to thoroughly.
That said, I really liked the book! The structure is clear and set out in a way, that doesn't get to dense with complicated to understand things. The text is written in a prose that gives motivation for why things the way they are, context for what you have to look out to and insight to newer developments/experimental features. It's a nice read, the examples are well chosen as well. Can't really complain, except maybe that even more diagrams here and there would be nice (e.g. with the "ABA" problem).
My only concern and caveat that I would warn you off: Like you know already, technology
(especially in computer science) advances at a unprecedented and increasing pace - this book is no exception. It only covers features up to C++17, so newer features like std::jthreads, std::stop_tokens, as well as semaphores, latches and others are NOT included in the book. With C++23 just having dropped and C++26 being in its first stage of concepts, you miss out on (at this point in time) two versions that among other things expanded the multi-threading standard libraries. A newer version for the book is not planned/announced to my knowledge, but hopefully one will come out eventually.