What is Reamde? It starts by sketching out the idea that a World of Warcraft-like game can be used as a hub for real-world economic transactions, investing the pretend battles with actual human consequences. Then it becomes something different, with spy novel and crime novel overtones. Some of the action takes place inside a computer game, but not in a sci-fi way -- it's real people using a game as a tool in a realistic way. There is no magic, no science that doesn't actually exist right now (except for maybe an unrealistically advanced algorithm for modeling geology, a gag that is not essential to the plot), and no interaction with historical figures. And yet I think this is among Stephenson's most genre-specific works -- it is a Tolkein questing novel.
Because, when you think about it, what is The Lord of the Rings about? (Bear with me here -- I haven't read that series in over 30 years and I only watched one of the movies and part of another on a plane.) On one level, sure, it's about a ring and a dragon and magic. On another level, it is just about a diverse group with little in common other than a suddenly urgent goal. So the hobbits and the warrior men and the elf and the dwarf and the wizard form a fellowship to throw the magic ring into the fire mountain, thereby keeping the orcs from overrunning the world. And Reamde is basically the same story -- the tale of a hobbit and some warriors from antagonistic tribes and an ogre and an elf and a fairy and a wizard fighting against a bad wizard and his orc army, except that instead of magic and middle earth, they're recognizable people in a recognizable world.
Reamde, incidentally, is the third questing novel I've read in the last couple of months, having been through Lev Grossman's The Magicians (recommended) and The Magician King (less recommended). Those books, it seems to me, share Reamde's goal of modernizing the questing novel, but in a different way. Unlike Stephenson, Grossman overtly adopts the magical trappings and tropes of the Tolkein-Harry Potter tradition, but invests them with a meta self-consciousness and an early- postadolescent petulance. Reamde is Tolkein for people who don't believe in magic; The Magicians is Garden State for people who do.
In other words, I just wrote about Neil Stephenson, Tolkein, and magicians. I am exhausted by my nerdness.