Last year, I recommended the 1995 documentary, Crumb, to a friend, but couldn't find it anywhere. I notice that it's available now for instant download/streaming on Amazon video. I highly recommend it to anyone who has an appreciation for psychology, personality and/or documentary film.
Robert Crumb, for those who don't know, is an artist and pioneer of the underground comix (small press, self published) movement. If you're of a certain age, you cannot have not seen at least some his work because it was everywhere back in the 70s. I won't offer psychological commentary on the man, except to say that he's a fascinating character. And, IMO, this has one of the best reveals I've ever seen at the end of a documentary.
If your puritanical streak runs deeper than your curiosity about the mind, you may have a hard time with this film. Otherwise, as the Amazon blurb says, it's "a wild documentary ride through the mind of artistic genius and sexual obsession."