Flatland, by Edwin A. Abbott, is a memoir written by one A. Square, who inhabits the two-dimensional universe known to us as Flatland. The first half of the book is about Flatland itself, and the lives of the people inside it, who live in a strictly ordered society where social class is determined by the number of sides you have. Women, all of which are lines, have the lowest status (even though they are technically really thin quadrilaterals). There's also this freaky thing where kids are beaten into being more regular, and color is not allowed, and it's kind of terrible.
The second half of the book is about A. Square's experience of being visited by a Sphere from Spaceland, which has a third spatial dimension. As A tries to wrap his head around the fact that there can be a third dimension, the reader gets to try to thing about what a fourth dimension could mean. The Sphere also takes A through the first and "zeroth" dimensions, which is fun. Then the Sphere takes A back home, at which point A is promptly thrown in jail for being a lunatic. If you like dystopias and/or thinking about higher dimensions, then Flatland is a book you might like.