The best book on the topic I've found. And I'm in fact hooked on the subject, so bear with that :)
Here are my reasons:
1. The authors do a lot to carefully describe all the hard concepts one by one, in order, w/o getting bound to any particular implementation. This is not easy and twice or thrice I made a mental note that "I'm missing X here, if I were him/her, I would write about Y", but to my satisfaction, these deficiencies were always fixed in further chapters of the book.
2. I like the comparisons between traditional (centralized) and self-sovereign models - and the fact that the authors were transparent about challenges in front of SSI, BUT sometimes I missed more practical (that's the key word here, because there are many very theoretical ones) examples and indirect challenges (especially for governance and proofs).
3. Chapters 7 and 8 (the two most important ones) could use a bit more polish. I'm not sure everyone will comprehend them at the first read and they are crucial to understanding the whole book.
4. I think it would be good to create a new, separate chapter for "devil advocacy" - to deal with the common statements criticizing the concept of SSI.
5. My favorite chapters: 17 (parallels between identity and money), 3 and 5 (as they set a nice conceptual foundation for the whole book). My least favorite chapters: 19-24 as I don't think they add much to what's covered in 18 (explaining the value of SSI to the business)
In the end: highly recommended. I strongly believe that the concept of SSI will be extremely important in the future - that's actually one of the few implementations on the blockchain that make a lot of sense. Fortunately, this interesting topic has got a very good book - the one it deserves.
Strong 4.7-5 stars. A-MUST-READ.