Neal Stephenson recently gave a talk called The Fork: Science Fiction versus Mundane Culture at Gresham College. It's an interesting talk, and one of the things he talks about is how genres have evolved over time. Fifty years ago, there were a lot of fairly well delineated genres. He gives some examples like Romance, Westerns, and Crime. Westerns have basically disappeared. It's still a genre, but anything produced in that genre happens in some exceptional way (I think the genre survives because it has a rich history; otherwise it would have disappeared completely). Romance has more or less merged with all the other genres. Sure, bookstores still have unabashed romance sections, but you don't see much of those stories elsewhere in movies or television. Instead, you see romance merged in with just about every other genre. Most movies feature some romantic element these days. There are exceptions, of course, and there are sub-genres that are more romantic than not (i.e. romantic comedies), but for the most part romance on its own is pretty rare in movies. In a way, romance has become so ubiquitous that it ceases to be its own genre. Similarly, crime stories have become so commonplace that it's barely retained itself as a grenre. This is especially the case in television, and I can guarantee that there are at least 3 or 4 separate episodes of Law & Order and/or CSI playing on television right now, as I write this entry. Stephenson goes into more detail for all of these genres, and it is quite interesting.
A while ago, I linked to an article that featured a bunch of SF authors attempting to define the science fiction genre. I didn't talk much about my thoughts at the time, except to say that I favored a more broad definition than most of the authors, and part of the reason I did that was because of Neal Stephenson. He became famous for novels like Snow Crash and The Diamond Age, obvious and unabashed science fiction, but his later works have curiously moved into more of a historical fiction. Crytponomicon takes place partially during WWII (with the other plotline being in the present day) and The Baroque Cycle takes place entirely in the 17th and 18th centuries. Both stories feature a lot of science and/or math, but they aren't your steriotypical SF. There's nothing futuristic about them, they don't take place in space, they don't feature aliens (well, we don't exactly know what Enoch Root is, so perhaps I'm wrong about that - then again, I don't think I ever want his character to be explained). Basically, a lot of the more strict definitions of SF would exclude those books. As such, I've always been curious to see what Stephenson's thoughts were, and perhaps unsprisingly, he seems to hold an extremely broad definition of what constitutes SF. He seems to embrace the notion of SF as meaning Science Fiction but also Speculative Fiction, which opens the doors to a lot of seemingly non science fictional things. For instance, he notes the way that science fiction and fantasy are often conflated, and he also seems to include anything influenced by comic books, video games or martial arts films as well. He also quotes Bruce Sterling's hilarious definition of "thrillers" (which funnily enough, involves science fiction). Is his definition too broad? Perhaps, but I think it's also a part of his larger point, which is that genres are kinda meshing together.
It's an interesting talk, and Stephenson goes into a lot more than just genre talk here, including stuff about vegging out and geeking out (which is something he's written about before) and the way most people seem to have become geeks in one way or another (geekhood no longer seems to be limited to computer enthusiasts).