OH Boy, I never knew that Capote wrote "Breakfast at Tiffany's" which I loved as a movie! BTW, you are right about the true crime novels, but I thought he sympathized a bit too much with the criminals rather than the family they slaughtered.
It's been years since I read it (in high school) but I also remember being repelled by his graphic descriptions of the kid's murders. Seemed to take too much enjoyment in it.
The book Breakfast at Tiffany's is a lot different than the movie. However, one bit of trivia about the movie -- Capote insisted (fought actually) that Hepburn should sing Moon River. Another bit of trivia, which may or may not be true, Capote never attended college. But he did get a job as a lowly clerk at The New Yorker. One of his supposed duties was helping a very cranky James Thurber get dressed after meetings with his mistress. In a fit of vengeance for the unpleasant task, he helped a nearly blind Thurber put his socks on -- inside out -- to tip off his wife.
Oh yeah, Capote was repelled by the killers and the murders. But the thing is, he was fascinated by secret lives -- the things that are hidden from view. This may be from his upbringing in a small southern town or being an outsider most of his life.
The guy really is interesting and very much like Fitzgerald and O'Hara in many ways.