I would rank an Arthur C. Clarke novel right up there with some of the great, most thematic works of all time. Science Fiction isn't just books, though. Movies, television, and especially the Internet have wide offerings of Sci-Fi fare. Here are some of my favorites. A Beginner's Guide Well, I'm glad you asked.
Many works have elements of both.
Some have attempted to place Star Wars in the Fantasy category. I think that SW is most definitely Science Fiction as well, even though it is based on speculative science. Star Wars is in the middle ground of Science Fiction and Fantasy. Fi, it is also not the primitive magic-lands of traditional Fantasy. Science Fiction has its roots in the works of Jules Verne and H.G. Wells.