Flatland: A Romance of Many Dimensions by Edwin A. Abbott
Published in 1884, Edwin Abott Abbott’s Flatland is a hilarious romp through a rigidly structured two-dimensional society populated by lines and other geometrical shapes. The storyline is built with a sublime, intuitive exploration of the mathematical concepts of the first through third dimensions. In the end, along with the characters, we are invited to conceptually grasp beyond those first three dimensions.
Carl Sagan gives the best explanation of Flatland in this clip from his classic series, Cosmos.