*Second reading* I read this for the second time this year for my qualifier/comprehensive exam, which loosely covers Chapter 1-6. I think this time I could grasp a lot of ideas better, as it should (now that I am second year PhD).
What I have come to feel is that this book is somewhere in between rigorous GR texts and physically intuitive GR texts. Bob (Wald) tries to go beyond standard "introductory texts" by covering as much ground as possible in as concise, physically sensible manner as possible. Naturally he had to pay a price: fewer exercises (which are not so trivial), and sometimes rather opaque statements (whose details are left to the readers). I think this is the best he could do to be more technical than most books but without converting this into a pure mathematical GR textbook. The arrangement of technical requirements like manifolds, topology, symmetries into the Appendices is a very clever idea (and convenient).
Overall, I think this book is *not* for learning GR the first time, unless you simply love challenges. I would recommend readers to pick easier textbooks, or better still, take an actual course with lecture notes that are well-written, before using this book (or keeping this as a -reference text-). For instance, I think what made me able to learn more was after taking courses, and reading Harvey Reall's lecture notes in GR.
This is a good book to keep as reference text. You will find most of the ideas you need for GR here. But for more details, explicitness, and newer contents, or even exotic ones (like wormholes and time machines), you will need to go beyond this.
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Technically done a while back, focusing on chapter 1-6 and chapter 8,9, and 12. Also appendices. The rest are very specialized topics which may not be useful to read unless you work with them directly.
Didn't really do the exercises, but rigour is definitely there and the book serves as excellent reference where you could simply find what you need inside, and whenever details are omitted you will know how to look elsewhere. It's the book you will keep for many years possibly till you stop doing relativity.