Wonderful mindfuck of a book by Robert Anton Wilson. Basically, it's Timothy Leary's eight-circuit theory of consciousness expanded upon. The first four circuits are an extention of Freud's stages of psychosexual development, the last four get kind of quantum-mystical.

What the Thinker thinks, the Prover proves!

This book forever altered my brain, for better or worse. In addition to Leary, it turned me on to Nikola Tesla, Wilhelm Reich, various conspiracy theories, Hakim Bey, chaos theory, Aleister Crowley (or was that Ozzy?), James Joyce, and whole bunches of other weird shit.

Be forwarned: if you enter the Chapel Perilous that is your soul, you may only exit insane, enlightened or dead.