Thematics: the first book gave us the (long) price of slavery -- from several angles, each rendered as an abusive relationship. (Cruelty; internalized self-hatred; the generational passing-along of child abuse.) This book is then the price of patriarchy: the Khaiem's treatment of women, and of male children, rips the crap out of everybody.
Our friend Otah Machi -- not inconsiderably canonized by the narrative -- attempts to save everybody. (Everybody who's left, anyhow.) The fact that he more or less succeeds at the end of this book bodes really poorly for the next one. I theorize that these first two books form a story-arc rather like The Lord of the Ring -- a victory in their own context, but really just a story beat in the tragedy of their history.