FWIW, I found this book to be an extremely disappointing introduction to Neal Stephenson and an extremely disappointing exploration of Sulfur-based geoengineering. The actual geoengineering is just a vehicle for a semi-political thriller IMO.

It's not a great book, but the fact that a single billionaire could decide to change the climate with a relatively small amount of SO2 was news to me until I read this!

I felt exactly the same way. It seemed like he thought "If Elon Musk tried to stop global warming, what would happen?" and then just sorta fleshed it out an released it during his spare pandemic time.