Bob Shaw wrote a duology "The Ragged Astronauts" & "The Wooden Spaceships" in which the ratio of a circles circumference to it's diameter is 3. As far as I can

Bob Shaw wrote a duology "The Ragged Astronauts" & "The Wooden Spaceships" in which the ratio of a circles circumference to it's diameter is 3. As far as I can tell, the only reason this factoid is included is to defuse any arguments about the plausibility of other elements of the setting (a binary planet with a shared atmosphere such that it is possible for a feudal society to stage an invasion from one to the other using balloons). Celestial Matters by Richard Garfinkle has Ptolemaic cosmology and Aristotelian physics. The Planiverse: Computer Contact with a Two-Dimensional World by A.K. Dewdney is sort of a modern take on the classic Flatland by Edwin Abbot, and manages to improve upon it considerably. The Long Earth series by Terry Pratchett and Stephen Baxter posits an infinite set of parallel Earths that can be reached with a trivial but unorthodox electronic device. You have to travel to them incrementally, one sideways step