Anathem was my favorite book by him. It has a lotta re-read value, I appreciate the work he did to make it feel like a complete, fleshed out world. But different folks have different tastes, and that's ok.

I also liked Seveneves, but it should have ended 2/3 of the way through. There was a point that would have made for an excellent ending (which is something Stephenson famously struggles with IMO), but then he forced in another 1/3 of a book that didn't engage me and which felt like it just petered out.