Orphans of the Sky by Robert A. Heinlein
Hugh Hoyland is a Scientist on the Ship. The people who live there worship the Jordan. The society is agricultural. The ship is divided into farming communities. Above are the higher areas of less gravity. Only the Scientists can read or govern the people. Only they are allowed to read the laws of Jordan or to go up higher.
Hoyland is part of a scouting group that goes up above to try to get rid of the muties. He is instead captured and made a slave. Joe Jim is the two-headed mutie that becomes his master. Through Joe Jim, Hugh learns the truth about where he lives. He wants to be able to return to his people and reveal what he now knows. If he can get away from the muties, will he be able to convince the Scientists? He knows they have a destiny. He needs to prove the road his society needs to follow.
This is classic, early Heinlein. He takes a society that knows nothing but the interior of a spaceship. They have lived there so long they no longer realize they are inside a moving vehicle. Heinlein takes the rebel, Hoyland, to show the reader how easy it is to get constricted in our viewpoints. We also learn that we can break out of them, although it isn’t easy. This was written in the 1930’s. The science is not described in detail, and is still feasible. This is enjoyable, not powerful, Heinlein.