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Games based off novels!
(hexbear.net)
Tabletop, DnD, board games, and minecraft. Also Animal Crossing.
3rd International Volunteer Brigade (Hexbear gaming discord)
Rules
Too many to count based on Journey to the West (Dragon Ball would count too, I guess)
It's a short story and not a novel, but I Have No Mouth, and I Must Scream
Ubik, based on a Philip K. Dick novel
There's a bunch of games based on Dune, although the first one is based more on the David Lynch movie
A whole Discworld adventure game series
Hitchhiker's Guide to the Galaxy, a text adventure that's just about as wacky as the book
There's shockingly only one game based on Neuromancer from the 80s, it was made by Brian Fargo of Wasteland and later Fallout fame
This one's especially worth noting since the original author also wrote the game!