Interstellar space travel, alien invasions, nuclear holocaust, and futuristic computers; what do all of these thing have in common? They are all elements found within science fiction literature. We looked at the history of science fiction in our last installment. Many works of science fiction fit nicely into a well established set of sub-genres, while others defy classification in their uniqueness. We already looked at several types of science fiction in our article on the ‘Punk genres (such as Cyberpunk,) but there are many more to discuss. In this installment in our genre studies series, I will be covering some of the broad classifications used to define works of science fiction literature.