Schopenhauer has been the most shattering/enlightening/disgusting read for me. Try "Aphorisms on the Wisdom of Life" for starters
Others:
American Psycho
Blood Meridian
Notes from Underground - Dostoevsky
Barnaby Rudge - perhaps surprisingly, but this is Dickens at his most extreme... example (slight spoiler): one anti-hero ties his employer to a chair and destroys his home and workplace around him, shattering his mind; then he sets fire to the mansion house of the local squire while dragging two young ladies off to a world of sex slavery... (What the Dickens!)
"Life is not really given to us to be enjoyed, but to be overcome, to be got over." - Schopenhauer.