Yup it's a great introduction as you can fly through it (3-4 hours to read most of it), at least if you already have a grasp of networking, linux, processes, threads, containers etc.

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 :-)