Dystopian Literature; Science Fiction
In case you hadn't noticed, the world of Snow Crash is not a nice place to live. Racism runs rampant, there are no longer any national laws to prevent killing innocent people in the crossfire of gang warfare, and your wealth may be the greatest indication of whether you've got a shot at living your life in something other than a storage unit. So without further ado, we're going to go ahead and label this one dystopian literature.
We also feel pretty confident in calling Snow Crash science fiction, even though the "science" parts aren't too ahead of today's technology. We're still waiting on a reliable and accessible version of virtual reality, sure…but think about it this way: the science in the book is integral to the plot. No Metaverse, no programmers, no neurolinguistic brain hacking, no plot.
Depending on who you ask, Snow Crash is an example of a subgenre of science fiction, cyberpunk (or if you wanna get technical, it can also be considered postcyberpunk). One definition of cyberpunk is "a combination of high tech and low life." One look at the characters of Snow Crash illustrates that phrase perfectly: skateboarding street-scum with high-tech gear interact with underemployed sword-wielding hackers. The cyber (short for cybernetic) and punk mix perfectly in Stephenson's wacky characters.
Another definition of cyberpunk lists some key traits of the genre: the negative impact of technology on society, corporate control over society, fusion of man and machine, story focusing on the underground, and so on. Even if you've just skimmed the book, you should by now be able to read each of these phrases and think of a way in which Snow Crash exemplifies it, perhaps many times over. If you dig this instance of cyberpunk, consider checking out all the other cyberpunk literature out there.