Flatland is a sort of metaphysical novel that uses the concept of higher dimensions as a metaphor for transcending a rigid class structure. The main character, A. Square, has lived his entire life in a two dimensional inhabited by simple geometrical shapes and in which one's social station is determined by the number of sides you have. Sphere lifts Square out of the world he has known into a three dimensional world and all of Square's ideas about the nature of reality are blown away. When Square suggests that they move on to the fourth dimension Sphere tells him there are only three dimensions. The reader suspects that although Sphere's worldview is bigger than Square's was Sphere is also bound by rigid ideas. A fascinating little novel of ideas.