Neil Stephenson's postcyberpunk classic. What defines postcyberpunk isn't clear, but this is definitely it: Stephenson invents a world that's an anarchistic parody of hyper-commercialism, populates it with a large cast of completely ridiculous characters, manages to send up pretty much every convention of the genre, and yet weaves an utterly compelling story that'll keep (at least a certain class of) readers entranced. I'm not convinced that I'd want to live in the Neuromancer universe, but I'd feel right at home in Snow Crash's world -- and especially in the Metaverse.
It's been a while since I last read this, which meant that I spent most of the time happily rediscovering good bits that I'd forgotten. I still think the introduction (which I won't spoil for those of you who haven't read it) is the best I've read in any SF book, and the "chase scene" bit has made me laugh out loud every time I've read it so far.
Thoroughly recommended -- indeed, if you haven't read this book, you're missing out.