Slow moving, but ultimately worthwhile. If you like political intrigue and the idea of assassin nuns, then I'd definitely recommend this. 
 The interweaving of the magical/fantastical elements with the historical side of this was really appealing. I like the world and myth LaFevers builds here--especially since she uses the narrative to pose some really interesting questions. Questions about choosing your own path, about obeying orders blindly and about compassion and mercy. 
 Ismae is an interesting character as well, though she does sometimes fall into the trap of "I can't possibly be a 'girly-girl' because I'm tough and can take care of myself". Which, all right girl, we get it. You literally are an assassin. But cool it. 
 Though I am a little baffled by the (view spoiler)[magical healing vagina thing. No, I mean literally. She counteracts the poison in a man's body by having sex with him. (hide spoiler)]. I mean, I guess, but really? When I realized where that was going I sort of had to put the book down for a second in bewilderment. And then laugh at the absurdity of it. Not that I don't appreciate the trope-reversal on one level but still! 
 Anyway, a good book and a series I'll be interested in checking out from the library.