This book is really interesting and I will definitely work on implementing some kind of Zettelkasten, Evergreen notes (notes.andymatuschak.org/z3SjnvsB5aR2ddsycyXofbYR7fCxo7RmKW2be) or other PKM solution.

The book is small, the idea is interesting, but the reading is cumbersome. As with many other "How to" books it is repetitive in form and in content. I think the base ideas are outlined in the first 30 pages and repeated with examples in the next 150 pages. And the examples are repeated two and three times.

There are a gazillion blog posts about this that resume it in a 10 minutes read. If you only want to implement your Zettelkasten better go for them. The book is good as a source of references and bibliography.