The more of The Broken Earth trilogy that I read, the more I'm convinced that N.K. Jemisin is the best possible response to grimdark fantasy. The apocalyptic world of these novels is, I would say, bleaker and more disturbing in concept than anything in the works of George R.R. Martin (Jemisin even does a very effective line in body horror), but the story is so firmly rooted in sympathetic human characters that, even as the world crumbles around them and they are forced into terrible, bleak, tragic situations, I never feel the weary grind of nihilist despair settling upon me (Why hello, A Song of Ice and Fire!). She balances a gritty ability to deal with heavy, important themes - like abuse and institutional racism - with a sympathy and humanity that prevents it from ever being overwhelming. In two books, Jemisin has kicked me in the feels more effectively than most fantasy authors, but the end result is still fundamentally more hopeful than the vast majority of epic fantasy out there. 
 The revelations of this middle volume are, interestingly, ones rooted in character. Nassun takes her own viewpoint, as does Schaffa, and they both turn over the tables of our conceptions in surprising and affecting ways. As a result, perhaps, this volume does seem a little light on plot progression. The end of the novel is even a direct callback to the end of The Fifth Season, and it's hard not to feel that much of the book has been the plot equivalent of a training montage (whilst engaging in a lot of excellent character work). Our characters have gained skills and backstory, and we've had quite a lot of intriguing exposition, bit it still feels like setup minus a conclusion. Then again, that's a pretty standard middle-volume-of-a-trilogy problem, and it bodes well for an explosive final book. 
 Yes, my copy of The Stone Sky is pre-ordered. Of course it is.