Like many others I thought this book was going in a YA direction at the start. The plot seems a bit on the nose for our anti-intellectual times. But the book takes a good dark turn when Lilith finds out that her father isn't the staunch defender of the faith that she thought, nor is her beloved mentor Kira. There is a sort of classic element here, in that it's when Lilith acts according to the principles her father upholds that she finds out what's really going on.
The book is pretty focused on protagonist Lilith's coming of age, so it's still very YA, but in a good challenging way. But the relationships in the story are mature. Not that kind of mature, you dirty-minded people! In fact, not that at all. A strong element in the book is that people who don't share goals or values end up having to cooperate, or tolerate each other. Those stories are very well drawn here, and it's not something you see that often in SF literature. Worth the time in my opinion, I got a lot out of it.