The other book I like is "C# in Depth" by Jon Skeet (2019). He has 2 chapters on the business of async/await. The second one attempts to dig into the implementation by using disassembly tools and knowledge of the IL. I admire this, and sense a kindred spirit. He wants to know what is going on -- and the details aren't explained anywhere -- so let's see what we can learn by prying the lid off the box and looking inside.
But I mention this, not just to recommend books and sections in said books that you ought to read, but to underscore that this is not a trivial topic.
Tom's Computer Info / tom@mmto.org