The Rule of Four

A 2005 novel written by Ian Caldwell and Dustin Thomason, about unraveling the mystery of a 500-year-old (real) book called the Hypnerotomachia Poliphili, with a murder mystery thrown in for good measure. Most of the action occurs at Princeton University, which occasionally makes The Rule of Four read like a campus tour guide/campus spirit flier. Nevertheless, it's an enjoyable book for cryptography or history buffs.

Not to be confused with Rule 34.

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Tropes used in The Rule of Four include:

• Ancient Conspiracy - The Hypnerotomachia's backstory. Also contains elements of Beethoven Was an Alien Spy.
• Contrived Coincidence - The story takes place a few days before Graduation, but the characters are able to escape the campus cops by blending in with a public naked party to celebrate the first snowstorm of the year. Graduation is in May, that would have to be an extraordinary year for it to be the first snow in New Jersey.
• Follow the Leader - Arguably rode on the coat tails of the far more successful Da Vinci Code.
• Ivy League for Everyone
• Knight Templar - Girolamo Savonarola
• Linked-List Clue Methodology - The Hypnerotomachia's clues are solved one at a time, and each leads to a new puzzle.
• What Do You Mean Its Not Symbolic - The manuscript itself is a gigantic mess of Renaissance symbolism, and that symbolism is an important part of the decryption process. Think Neon Genesis Evangelion written by Leonardo da Vinci and you get a good idea.