Strikes me as a fix-up novel, that is several shorter works rather inelegantly glued together.
Spoiler!
Main story, rich gaming guy dies, his brain is scanned, stored in a cloud, and his niece switches it on. After many reboot cycles it/he gradually makes sense of its surroundings and creates a world, based on gamer logic, that is streams look like they run downhill and have waves all due to animation rather than gravity and fluid dynamics. After a very long time some other scanned brains turn up and things wander along in a more or less satisfactory fashion as they build a world. Then another really rich computer guy dies, he's bought faster computers and more storage and is more powerful than the first guy. The vast majority of the book is an epic quest by various early arrivers to overthrow the new boss. It's written in a mock epic grammar and is boring as batshit. There is a lot that is unexplained and it's a bit like reading a dream, never my favorite occupation (the Amber series was one of the few to pull that off).
However being Stephenson there's some good asides. One is a in internet hoax, well funded, that describes a remote town as being nuked. The outcome of that leads some more billionaire computer people to decide that the internet as is is busted, so they decide to really bust it by creating robot trolls that just sit there generating memes, fake news and random gibberish about any newsworthy person. Therefore it is no longer possible to rely on it for anything. As a result anyone who watches the unfiltered internet is buried in a vortex of self reinforcing fantasy. This leads to the best bit of the book where the Bible Belt of the USA reverts to Levitican law due to the self reinforcing fantasy bit, with various entertaining consequences. Back on the main story as the virtual world grows more and more of the Earth's resources are devoted to expanding it and powering it, such that the real world becomes almost parasitic to the virtual one. And it all ends happily ever after.
However being Stephenson there's some good asides. One is a in internet hoax, well funded, that describes a remote town as being nuked. The outcome of that leads some more billionaire computer people to decide that the internet as is is busted, so they decide to really bust it by creating robot trolls that just sit there generating memes, fake news and random gibberish about any newsworthy person. Therefore it is no longer possible to rely on it for anything. As a result anyone who watches the unfiltered internet is buried in a vortex of self reinforcing fantasy. This leads to the best bit of the book where the Bible Belt of the USA reverts to Levitican law due to the self reinforcing fantasy bit, with various entertaining consequences. Back on the main story as the virtual world grows more and more of the Earth's resources are devoted to expanding it and powering it, such that the real world becomes almost parasitic to the virtual one. And it all ends happily ever after.