couldn't read further than 'guts'...it was too disgusting.
If you read guts then you are done, that is pretty much the worse from the book (or his career) and from there on there are some really nasty things (losing your lips to frostbite, child sex dolls, pools of backed up sewage) but in part you are already desensitized and ready for other bad stuff.
Also a lot of stories are sleazy but ultimately clever, cute and funny. In particular there is one about a hippy masseuse who is taught how to give a man an orgasm with a foot rub and becomes a high class call girl, there are stories about ultra wealthy pretending to be homeless and about strange Marlyin Munroe murder/suicide conspiracies. Particularly great are stories about the apocalypse, bigfoot, a woman carrying a mysterious disiease and a knife endorsing serial killer which I remember as being pretty much pg-13 or even pg.
I do slightly recomend skipping the narrative between stories though, it is not bad but the book has so many stories that they had to draw out the main narrative endlessly. Imagine a movie about kids telling stories around a campfire and by the time they are done they are all grown up.
EDIT: Went to wikipedia and looked at the stories... with some lose standards I would say that only 7 or 8 are potentially nasty out of 19.