I am a huge fan of the "Explanations" page of their docs: "These explanation pages are oriented towards deepening your understanding of Hypothesis, including its design philosophy."

I feel much more software documentation could greatly benefit from this approach. Describing the "why" and design tradeoffs helps me grok a system far better than the typical quickstart or tutorials which show snippets but offer little understanding. That is, they rarely help me answer: is this going to solve my problem and how?