[The difference between the genres of science fiction and fantasy is that science] fiction is the art of the possible. There's never anything fantastic about science fiction. It's always based on the laws of physics; on those things that can absolutely come to pass. Fantasy, on the other hand, is always the art of the impossible. It goes against all the laws of physics. When you write about invisible men, or walking through walls, or magic carpets, you're dealing with the impossible. (p. 21)

I don't give a damn about the critics. I'm not interested in what they have to say. Really, I don't care about other people's opinions. If I did, I wouldn't have any career at all. I've been warned time and time again not to write science fiction by my friends, my teachers, and all the great intellectuals of our time. That's what's wrong with our...