As a fan of transgressive fiction, I've read quite a lot of fucked up books. Here's what I came up with off the top of my head - sorry, it's quite a long list!

Some different types of fucked up here (horrible fucked up and fun fucked up):

Cows by Matthew Stoke (not very well written, but very fucked up, a sick classic)

Anything by Carlton Mellick III, but especially Aspeshit, which is like Evil Dead on acid (semi literally). But he's definitely 'fun fucked up' not grotesquely nasty without humour. All Bizarro is fucked up and worth checking out.

Apocalypse Culture I and II are both intentionally fucked up compendiums of short pieces and art that will make you sick and angry, but also make you think about a lot of different things. Feral House have plenty of fucked up books that are worth reading.

Atrocity Exhibition by JG Ballard - experimental writing unlike most other Ballard books, but significantly more fucked up in parts. All Ballard is great and fucked up at some point; High Rise has one of the best opening paragraphs of any book, ever. Crash is probably second to Atrocity Exhibition in fucked-up-ness.

Marquis de Sade - Justine, 100 Days of Sodom. Juliette: (mentioned elsewhere) horrible imagination-run-wild in the worst way, but aimed at antagonising people against the aristocracy and satirising the extreme cruelty and nastiness of those in power, probably including himself.

UK publisher Creation books (and imprint Attack!) did "anti-books" as they called them - some fucked up stuff of all kinds there: from fun stupidity like Raiders of the Low Forehead to some really horrible stuff by Peter Sotos that was unreadable (even to me).

The Encyclopedia of Unusual Sex Practices by Brenda Love tells you all you need to know about human beings and a lot you never needed to know (eyeball licking fetishism is a thing, apparently).

Nick Cave's 'And The Ass Saw The Angel' is a wonderful pieces of fucked-up-ness and the reason for my username: a mute hillbilly recounts his sordid, psychotic life while drowning in quicksand, with biblical imagery and references, poetic 'Deep South' language, and lots of unpleasantness, especially from his parents. Kind of an ugly sibling to 'The Wasp Factory's.

Clive Barker's works can be pretty fucked up - Books of Blood is still his best work, in my opinion.

Supervert's 'Extraterrestrial Sex Fetish' was disappointing, badly written, and fucked up in boring but nasty ways. I'd avoid it, but it's a long time since I read it, so maybe I forgot a lot about it. I remember being bored and irritated, and little else.

Most Will Self books are pretty to very fucked up, particularly his early stuff.

Harry Crews was a wonderful writer, with some pretty fucked up stuff in Feast of Snakes and A Childhood - The Biography of a Place.

Chuck Palahniuk, Irvine Welsh, and William Burroughs all have lots of great fucked up work.

House of Leaves by Mark Z Danielewski is fucked up in terms of layout and typesetting as well as storyline. Some really effective parts, some get a little bogged down in their own cleverness. But very much worth reading. Not fucked up in terms of gore or sex, as far as I remember!

Patrick Suskind's Perfume is brilliant and fucked up, and possibly the only book that can change your sense of smell.

James Joyce - Ulysses and Finnegan's Wake are fucked up in terms of experimental style and language, and are wonderful pieces of writing, despite being notoriously 'difficult'.

Alejandro Jodorowsky's biographical books are wonderful and fucked up. 'The Spiritual Journey' is one of the best still.

That's enough for now - I'm sure I'm missing a lot!