Ask HN: What's the best documentation you've ever read?

I'm looking for examples of outstanding documentation such as The Rust Programming Language book: https://doc.rust-lang.org/book/ or The Python Tutorial: https://docs.python.org/3/tutorial/index.html

It doesn't need to be related to programming languages, anything counts: APIs, frameworks, some really in-depth blog post or series of posts, etc.

Sqlite's definitely high in the running (https://sqlite.org/). Feels like as much thought and care went into the documentation as the software itself.