by far the best documentary, and just film in general, that has ever been made about roller skating, the culture, the history, etc. nothing gives people on the 'outside' such an intimate introduction to our world like that film does. please give it a watch, you will be blown away.
as for books - there is a book that was published this last year called "the evolution of skating: live, love, sk8 to tell it" by amirah palmer, et al. it's a compilation of essays and stories written by skaters about the history, the culture, etc. i bought it for my boyfriend for his birthday and it's an incredible read. not too expensive and easy to read! it was also published as a result of the pandemic and rinks being shut down, so you should definitely check that one out as well.