The Eye in the Pyramid

The first book of the Illuminatus! trilogy, detailing the journeys of Hagbard Celine in the yellow submarine Lief Erikson which mysteriously changes it's name to Leif Erikson in the two following volumes, The Golden Apple and Leviathan.
Written by Robert Anton Wilson and Robert Shea in 1975, this was one of the earliest books to prominently feature discordianism, and it is also wickedly funny.
Information about the whole work is at the Illuminatus! trilogy, information about the meaning of the title is at eye in the pyramid.

The eye in the pyramid is one of the reasons I will not keep US singles on me.

I'll be walking through the mall or something, and I'll see (for the sake of argument) a pack of gum. I want it, so I'll take it off the shelf, bring it to the counter, smile at the clerk, and take out my wallet. I pull the wallet sides apart and...

It's LOOKING at me, Ray.

It will just stare at me, mocking me. It says "Go ahead and spend me, and I will haunt you for the rest of your days", but not in so many words.

My hands tremble as I pull the dollar bill out of the wallet, and the eye keeps its evil gaze upon me. My hand is now shaking as I attempt to transport the dollar from my wallet to the counter. The clerk asks if I'm okay, to which I can only reply with a horrified look.

I place the dollar on the counter, eye-side down, to see former president George Washington staring at me. His stare is different - that of compassion. Understanding. He seems to communicate through his gaze, as if to say "I know what you're going through. That disembodied eye is one of the creepiest things I have ever seen. Thankfully, I can only see it when placed next to another bill - and there's only a 50/50 chance of meeting the eye."

George's comfort is brief, as the clerk picks up the bill from the counter. The eye is BACK. It looks angrier than before, and is staring right at me!

I run screaming from the store, leaving a confused clerk with a dollar and a pack of gum.