Posted today on /r/AskReddit/: "What book fucked you up mentally?"
Animal Farm -- "The whole thing spooked the shit out of my 13-year-old mind."
Night -- "A candid, horrific, and deeply poignant autobiographical account of [Elie Weisle's] survival as a teenager in the Nazi death camps."
American Psycho -- "Absolutely nothing like the film."
House of Stairs -- "One by one, five sixteen-year-old orphans are brought to a strange building. It is not a prison, not a hospital; it has no walls, no ceiling, no floor. Nothing but endless flights of stairs leading nowhere--except back to a strange red machine."
Machete Season: The Killers in Rwanda Speak -- "Professor: 'I choose a book every semester to scar the students' Mission: accomplished"
A Child Called It -- "for a 7th grade book report. It's a very graphic memoir about child abuse. After turning it in, I got sent to the guidance counselor."
The Bell Jar -- "I never knew what depression sounded like before. 'To the person in the bell jar, blank and stopped as a dead baby, the world itself is a bad dream.'"
Flowers for Algernon -- "Read it in one sitting and was broken for like 48 hours after reading it.
Johnny Got His Gun -- "is horrifying"
My pick is Level 7 - a 1959 novel. I read it in the 4th grade. It's about the last people on earth living in a deep underground military bunker after a nuclear holocaust.