Which book would that be, out of interest?
The CNCF ecosystem looked a lot different back then.
Then you can hit other resources (in my case working with a team who've been using K8S for a few years).
If you (or anyone else) has suggestions for something newer and covering more than just the core (like various different components you can use, Helm, Argo, ISTIO etc etc) then I'd appreciate it :-)