 This is a true classic written in the 1880s by an English school teacher named Edwin A. Abbott. It is an autobiography written from the point of view of A-square, literally A-square, Mr. A-square. A two-dimensional entity in the shape of a square who lives in a two-dimensional universe in a society that is severely divided into a crushing caste system where a person's status is determined by how many sides he has. And women being nothing more than straight lines, of course, are on the bottom. It is a socio-political satire that belongs in the ranks of Gulliver's Travels. But it is also an exercise in mathematical and multi-dimensional thinking. Mr. Square is writing from his prison cell where he has been condemned as a heretical lunatic for telling people about a visitation he received from a three-dimensional sphere. As Mr. Square talks about his revelations on viewing and imagining a three-dimensional world, he teaches the reader to exercise your abilities to think about what a four-dimensional world might be like. Like I said, this is a true classic. People should be reading this not only in math and geometry classes, but in literature. An interesting bit of trivia, Edwin Abbott's middle name was also Abbott. So his name was Edwin Abbott Abbott, or AA, or A-squared. Get it? Also, in 1965, there was a sequel called Sphereland, which was written by Dionys Berger. It is about as perfect a sequel as you can get. It continues the adventures of the Flatlanders, specifically the grandson of A-square, who is a Pentagon. History had progressed much like our own world, so that the caste system was pretty much gone. The status of women was greatly improved. Science and exploration of Flatland had increased dramatically. And of course, the mysterious sphere makes another visit. There is another book by Rudy Rucker called Space Land, published in 2002. And there was also a very bizarre variation on Flatland, published in 1982, called The Planeiverse. Flatland has had a great influence on science fiction in general. It really is something that you should read.