The book covers the basic topics with good examples and I only miss more information about ZFS.
But it worths the cost because is a perfect guide for beginners and advanced users that explains you all of the topics that you need for have a complete Proxmox cluster and show a lot of real scenarios with different architectures at the end of the book.
When you read this book you are able to manage a complete Proxmox cluster with Ceph storage cluster.
The second recommendation for all of you that are interested in DevOps culture and automation tools is Configuration management with Chef Solo (Naveed ur Rahman) that has been reviewed for my colleague Jorge Moratilla and covers an easy and useful way to manage your platform without client-server architecture.
Ideal for people with basic ruby and sysadmin knowledge to progress with automation tools if you know the basic topics about thata dn you have some experience with this kind of tools.