Entertainment value is good, but I must press you to be much more specific. Let me just say a lot of science fiction is "imaginative," and there's a lot of science fiction. You don't have all the time in the world, and there's plenty of writing that's imaginative, but will still seem like crap to you -- or at least not as good as some other stuff you might be reading. Anyway, what do you mean by "imaginative?"
I have never read very much Science Fiction, unlike some of the people here on Less Wrong, and I think I would like to. At least, the few books I have read I enjoyed. I've read a couple of books from Asimov's Foundation Series, two Michael Crichton books, Twenty Thousand Leagues Under the Sea by Jules Verne, and an anthology of SciFi short stories (no really famous authors) that my dad owned.
That list looks very short. I just finished reading a fiction book, and am looking to start another. Recommendations? What are the two or three books I simply must read?