The Sunless Countries
io9 gave the book a great review, saying among other things:
“Other books in the series have dealt with rebels who want to build their own suns, and the political machinations of the great nations near the center of Virga. But The Sunless Countries is a standalone adventure that takes place at the periphery of everything: In a history department at a university in the sunless nation of Sere. Specifically, it concerns the strange adventures of a rebellious history researcher named Leal who is caught up in an ideological battle against intellectuals within her own nation—as well as a battle against all of humanity being waged by mysterious creatures from beyond Virga's skin.