I'm of two minds with this one. 
 The things it does well is very, very good... but when it came to my own preferences, I got bogged down in a good and nice long rut of boredom. If I was someone else, someone who really enjoyed a lot and a lot of YA school stuff, then I'd probably go ga-ga over this. 
 As it is, I enjoyed the writing and the developments, albeit slow developments, of the story. 
 Sure, it's awesome that it's a school of assassin nuns and the Ancestors and the hints of high-tech and moving moons and all that stuff is pretty cool, but it wasn't Harry Potter and there wasn't a lot of other things going on. The huge arc was all about the chosen one and some of the nuns were rather memorable... I'm thinking of you, poisoner... and yet, there was something about it at around the mid-way point that made me lose interest. The big actions and reveals were downplayed by the resumption of more studies, or perhaps I'm just a bit inured to it. 
 On the other hand, when the magic comes out and the climax arrives, I'm back in the story's skin and it got good again, so I still call it a win. Maybe not the best fantasy I've ever read, but the writing is solid and everything is pretty well-developed for most tastes. 
 It's just the fact that I've read a ton of really great fantasies in the last year and this is a bit middle-of-the-road. Still decent, though!