The non-game design books that influence my game design include:

Understanding Comics by Scott McCloud. Not just for information theory, but for how to take a medium, break it down into component parts, then use those pieces to tell stories and convey emotions.

The Art of Language Invention by David Petersen. Presents conlanging in a way that seems very similar to the indie rpg scene. Explores how to make a fictional world seem real by creating an artificial series of rules.

Euclid’s Elements. Takes a small number of rules and spins out the logical consequences of those initial rules. The sort of logical elegance I want to recreate in games: a minimal number of initial assumptions creates a rich, complex world to explore.

Any collection of Martin Gardner’s math articles from Scientific American. Playful and creative and eye-opening.

High Weirdness by Mail by Reverend Ivan Stang. A playful, sarcastic overview of the many strange beliefs people can hold.

(I originally posted this list elsewhere, on social media, but wanted to preserve it somewhere I could find it easily later on. And maybe other people would see it and find it interesting?)