I agree, re The Three Body Problem. It's a fun story, but not hard sci-fi in the way Stephenson etc are. I also enjoyed the dive into mid-century communist China - it was a jarring, immersive journey into living-memory history I hadn't learned about before.

I think Diamond Age was my favorite overall Stephenson story in terms of both story and neat scifi concepts, but all of them were enjoyable. I agree on Seveneves chars all being forgettable. Dodge (The most recent one) had perhaps the dullest start, but I really liked the Dodge, Corvis, and Daisy characters.