Somehow I'm never happy with CMake guides. The official book is ridiculously outdated among other things, the official documentation is complete and current but provides no guidance, and none of the blog-documentation about it gives a complete picture. Some of it is bad advice. This one doesn't talk about the dependency graph, something I consider very important in a build system. It is also missing a lot of other stuff. (Fair enough, it's provided for free.)

I wrote the CMake training material for KDAB (www.kdab.com) while I worked there. In my biased opinion it's the best CMake guide around, especially after it was extended and polished by coworkers :). I tried to mix explaining the "inner logic" of a build system, and CMake in particular, with examples, resulting in something I'm reasonably happy with. The main difficulty was ordering the topics to avoid too many forward-references while also not starting with a lot of not-obviously-interesting groundwork [1]. (I don't work there anymore btw, so the interest I have is getting my work used)

This intro to modern CMake should be good because Steve is a major CMake contributor and good at explaining. The presentation even contains a dependency graph! https://steveire.wordpress.com/2017/11/05/embracing-modern-c...

[1] Aside: I figured that "There are two types of bad software documentation: math textbooks and cooking recipes. The former does not explain why you are doing things and other helpful context, the latter won't help you if you need to do something differently, which is almost always."