This article hit a rare perfect note for me, I wish there was more documentation like this out there. Instead, the choice is often between very basic introductory stuff, API docs, and step by step "how to build a todo list" tutorials. What all those things miss is the theoretical motivation and the primitives that have been established to address that motivation. That's where I'm happiest starting when I try to pick up something new, since I feel that all the details snap neatly into place once you understand the ground level stuff, but to get this ground-level view I have to hunt for independent articles, online courses, or books, when it should exist in the official docs.