Quoted from loneacer:Dark Tower series
I cast another vote for The Dark Tower - King's magnum opus. Though by no means exhaustive, a few must reads (for me) are as follows:
The Catcher in the Rye (Salinger)
Anything by Vonnegut (Breakfast of Champions at minimum)
Walden (Thoreau)
Crime and Punishment (Dostoevsky)
Cathedral (a collection of short fiction by Raymond Carver)
Fahrenheit 451 (Bradbury)
A Clockwork Orange (Burgess)
The Picture of Dorian Gray (Wilde)
Waiting for Godot (a play by Samuel Beckett)
Leaves of Grass - Deathbed Edition (Whitman)
Marry Me (Updike)
The Stranger (Camus)
Shakespeare's Hamlet