Wow. Really loved this. Lyrical, evocative writing and glorious complex characters. Poses some interesting moral questions about the limits of power and the interaction between means and ends. 
 In its world-building this reminded me a lot of Ann Leckie's Ancillary series - the way customs and practises are portrayed as normal and not comment-worthy - but the plot is more intricately political and the action more visceral. 
 I'm really looking forward to the second one now :)