Do not miscast this wonderful little book as being merely "sci-fi". Two-dimensional "worlds" exist within ours, if only in a somewhat pragmatic sense. If we imagine some "thing" intellective within such a world, then we have little difficulty seeing that our humble narrator, Mr. A. Square, might be such a world's most insightful oddball. The book is a classic exposition in basic geometry, but it is more than this. Abbott uses mathematics to make some very telling observations about human minds and psychologies.
Edwin Abbott (1838-1926) was a clergyman and a math geek. He was an educator, an expositor of English literature and New Testament studies, a notable headmaster, and the author of something like 40 books on widely varied themes. Today you will probably have a difficult time finding any of his other volumes, but Flatland is said to have never been out of print since it was first published in 1884.
No need to retell A. Square's big adventures here, other than this bit of dialog between our two-dimensional thinker and his three-dimensional visitor/teacher (Square is given to thoughts of still higher-dimensional worlds):
"SPHERE. But where is this land of Four Dimensions?
[A. Square]. I know not: but doubtless my Teacher knows.
SPHERE. Not I. There is no such land. The very idea of it is utterly inconceivable."
Abbott offers his allegory of physical and conceptual limits with an economy of word and thought that is nothing less than extraordinary. A great many volumes, five to ten times as large, conclude having said far less than this little parable. Read it. You will take from it what you are willing to take. If you find little or nothing here, you are indeed a citizen of Flatland.