Johnny rescues a stray Pekingese and lets a woman take the dog home. However when she is driving away, she throws the dog out of her car window and he dies - very graphically.
There is a bit of discussion about different characters experiencing sexual assault as well as a character planning out the assault and murder of a woman, though it is unclear whether this event actually occurred.
Your not likely to come across it but if you decode the may 8, 1987 letter in the appendix II Johnny's mother talks about how the staff are sexually abusing her. Not very graphic but still very disturbing. It is also unclear whether it actually happened due to her psychosis.
Nobody is buried in dirt, exactly, but a person is buried and crushed in the labyrinth and being in the labyrinth is compared to being buried alive a few times.
It is a book, so no, but there is a frequent, unorthodox use of layout that can get very disorienting, meant to invoke feelings of claustro- and agoraphobia
I know this is put here because of epilepsy, so I don't think it counts, but it does include a lot of VERY manic, confusing, and all over the place writing that could incite a panic, so I put yes just to be safe?
Hard to explain, but the story presents itself as a real book that was published by the (fictional) characters in the book, attempting to blur the line of reality between itself and the real world.