....and no one ever mentions the third part because it was so long and poor that the book would be better without it.
Seveneves wasn't bad, but part 3 dropped it well down my list of favorites, maybe below Zodiac.
For context, an informal off-the-cuff ranking of his books for me:
Anathem (epic world building, I love the philosophy and the theory)
Cryptonomicon (I've always been interested in WWII, Cryptography, and Computers)
Baroque Cycle (taught me a lot of history I didn't know and somehow made finance interesting)
Diamond Age
Snow Crash
Reamde (not the most technical, but one of his best paced and a good thriller)
Zodiac (also a nicely paced thriller)
Fall (I don't hate this like some people do, but would love to see the real world from the beginning developed further)
Seveneves (I love the science and hate the pacing and all of the third act)
Rise and Fall of DODO (this felt like a slog to me and by the end I was forcing myself to read just to get through it).
The Big U (I don't think this is as bad as Stephenson himself does but it's nothing amazing)
Mongoliad (not my thing)
I pre-ordered a signed copy of Termination Shock, read the first few chapters, got distracted, and have never cared enough to go back. I suppose I should finish it but it didn't grab me fast like some of them have.