Battle Royale may seem like the obvious choice, but I'm going for it anyway. Both manga and book count really.
Highlights include a character who in the manga is shot with an Uzi across the stomach, causing his intestines to fall out and he's forced to try and keep them in, first with his hands, then with duct tape, then he has his foot shot off, then he gets machine gunned again, before finally being shot in the throat, and is still alive enough to carve a message with a toothpick into a metal car door for the main hero to read.
Other notable inclusions are eye-gouging and castration, all in the same scene, multiple head shots, dismemberments, and a scene where one deeply deranged female character has sex with a male character who is already dying of a gutshot wound in the mistaken belief that it can heal him.
Every single detail people, and in the manga it's been illustrated.
EDIT: Goddammit ninja'd!