2.5/5
2 for the content, and 0.5 for the effort.
TLDR: this book should have been a blog post.
I expected this book to be more like a textbook on SaaS multi-tenancy given the book size, but out of almost 500 pages, the useful content takes only a small fraction of that. The rest is neverending self-repetition, useless diagrams, and a lot of water with the sole reason of filling the pages with text.
The core of the book, namely chapters 2 to 9 + 10 (K8s) or 11(Lambdas), could have been a blog post. I tell you more, there are blog posts that do more than this book. There are articles on Kubernetes multi-tenancy that explain the topic much deeper and provide you with real-world examples.
Each topic starts with the author promising to give a deep inside look into a specific topic, continues with endless self-repetition and a very high-level overview of the topic, and finishes with something along the lines of "the challenge is that there are simply too many permutations of options to cover them all". Bang! Another chapter is done.
The last 3 chapters could be just 100 blank pages without losing much of the sense, but hey they added a chapter on generative AI so this should do the trick.
This is not a technical book by any means. There are no practical examples or references to any real architectures sharing the traits the author points out. The chapter on K8s misses some critical points on resource quotas and different tenant policies. The author takes it as granted to explain to you the business side of SaaS multitenancy (and does it very poorly), but at the same time fails to give a comprehensive explanation of things like different deployment, upgrade, and rollout strategies of tenant environments. Some important things like Service Meshes and OpenTelementry are mentioned for the sake of mention. God knows how many other important topics are there that the author just missed.
Given all the above and more, I cannot recommend this book for any starting or practicing software developer learning SaaS Multi-tenancy.
P.S. I pretty much see a correlation between the number of books O'Reilly publishes each year and the quality of those books. This is by any means a bad trend.