Update: Embarrassingly for me, my top book here came out in 2008, not 2012 as I initially thought! It's like I don't have an editor. But! I'm going to leave it, as a sign of the arbitrariness of some such and also because I really like it and people should read it. Think of it as the best books of the long 2010s, I suppose!
For my fiction book list I was pretty wide-ranging in terms of genre. With non-fiction though, I just like academic deep dives (whether written by people inside or outside the academy) a lot more than I like biographies, memoirs, or anything else. So I didn't try to force it. Below are the favorite things I read this year, which is also a shorthand for the things I found most useful for my own writing and thinking.
10. Ibram X. Kendi
9. Noliwe Rooks
8. Kate Manne
7. Melissa Gira Grant
6. Edward Baptist
5. Diane Pecknold, ed.
4. Christopher Achen and Larry Bartels
3. Matthew Desmond
2. Julia Serano
1. John Rieder
The notable omission here is Ta-Nehisi Coates. I went back and forth but none of his books were quite my favorite, though I love some of his individual essays. Matt Stahl's Unfree Masters was also on and off the list.
I suspect the top choice will occasion some bafflement, but I have no regrets. Rieder's book is brilliant and thought provoking and introduced me to tons of new science-fiction, including the work of Gwyneth Jones. Also, the cover is great.