Informative reference work. Dated in some ways from being written before wide cloud adoption. Bits about training up new members on sre tasks and the first 10 chapters that define terms that are useful.
The first chapters are great to learn about how to set up SRE principles. After that I would recommend to cherry pick the chapters you find interesting. On one hand the book is super complete and gives good insights in how Google manages SRE. On the other hand the book is dated (which makes sense since it was written a while a go) and very enterprise like. I think little companies in the world would set up SRE like this .
There is a subtle bifurcation between SREs, Security Engineers, Release Engineers and Classical Software Engineers in the initial chapters. It would be fun to get to do all of it at different points of time. Later chapters were more interesting.