1. You have a documentation page per function whose primary aim is to give a day to day usage example. 2. The documentation integrates an outdated comment system, with comments that seem to predate dinosaurs ... interestingly enough, when you have deeper question, it's often interesting to read them, half of the comments are terrible but it still helps. 3. The layout is well executed so that you quickly find on the page the high level explanations, the examples or the arguments documentation.
Regarding books: if I would have realized 20 years ago that I could have gotten most of those books from the public library I could have saved a lot of money. Lots of public libraries offer access to eBook services like O'Reilly's Safari books online... but the wealth of info on YouTube right now is staggering. You could go from zero to near PhD level CompSci just on the videos and material being published by major universities.
Otherwise, the Rust book is also up there.