I just finished reading a very old, apparently well-known cult classic known as Flatland, by Edwin A. Abbott (1884). My friend gave it to me as a going away gift (they were going away, and looking for a good home for it). After reading it (and enjoying it), I did the usual Googling around to find out more. Apparently it is cherished by mathematicians, authors, philosophers, and educators alike, and has been for well over a century. Since it is in the Public Domain, here is an HTML version, and various epubs on Project Gutenberg.
There is an XKCD comic referencing Flatland.
Carl Sagan, in his Cosmos: A Personal Voyage, episode 10, The Edge of Forever, used Flatland to help explain the 4th dimension and tesseracts. Note this came almost 100 years after its initial publication!
The Futurama episode 2-D Blacktop has an entire third act dedicated to it.
Marc ten Bosch‘s highly anticipated 4D indie game, Miegakure, is very much inspired by Flatland. He explains how in this technical video about the game. He also includes the original dedication of Flatland on the bottom right of Miegakure’s home page.