I’ve noticed from past comments that quite a few of our readers like science fiction and fantasy (yes, two very different fields, but many people like both, and I’m one). So after several posts recommending such books, can I turn the tables, and ask: What science fiction or fantasy books that aren’t widely known among science fiction and fantasy readers do you love — not just like — and would strongly recommend?

Please limit comments to this subject; I hope to have similar posts in the future related to other genres.

UPDATE: If you like a writer, please recommend one or two books by the writer; I’m sure that even among the best writers, there are books that you think are the best and books that you think aren’t quite as good.