This classic tells of a future where embryos are adjusted from artificial conception to be not only one of five castes, but to do particular kinds of work. They're made stupid to do factory work, everybody gets sleep teaching, and everybody is always happy through the use of soma. We find that not everybody is happy, though, and see how they are treated and how their lives change.
The really ironic part of this is that Huxley is warning us about how bad eugenics and castes are while being entirely sexist. The book stands up pretty well, and everybody should probably read it at least once.