I've always maintained that there are two types of science fiction. There's the "Star Trek" kind that does social commentary, and tries to get the audience to

I've always maintained that there are two types of science fiction. There's the "Star Trek" kind that does social commentary, and tries to get the audience to think about something directly by sidestepping the trappings of modern society. Then, there's the "Star Wars" kind that is basically a far-reaching exercise in world building that only has a plot so that you're not reading a technical description. Stranger in a Strange Land is perhaps the purest example of the former, because it's very meta: the thing Heinlein wanted you to think about is the very idea of preconceived notions and full understanding. He spends the first half of the book explaining that you can understand something intellectually without understanding it emotionally, and the last half systematically questioning more and more ingrained ideas (at least at the time) so that you think about them intellectually. Most of the list is the other type. I'll pick on Dune, since it happens to be number one on the list. Herbert introduces you to a universe that's really completely unlike any other conceived: people fly around in spaceships and have enormous mental powers, but there are no computers (they are illegal), people still fight with bladed weapons (all others are rendered either useless or too dangerous), and universal government has become feudal in nature (for various reasons). People send messengers. A bioengineering project and a social engineering project (gray projects by the same faction, no less) collide, and turn the universe upside down. As far as hard SF goes, I'd originally clustered that with the world-building type, basically because every good example I've read happens to be in that category. Now that I think of it, though, it's not strictly required. It's really just a question of how much effort they put into reasoning out the science.