Fun story, interesting magic (more on the fun side than a full magic system), good writing and story progression, and Baba Yaga/Russian folklore. The characters having... unsavory...flaws does make some sense in context but I think the pedophilia backstory was unnecessary and didn't add to the character or plot; it would have still been inappropriate and added the same character depth if they were both adults in the same situation. I disliked the animal violence, but it was at least in theme with the book, characters, and situations. 
Spoilers: I think the ending was grasping at something that could have been cool if the author had spent more time exploring concepts of gender, non standard/poly relationships, attraction, and sexuality. Without more depth it felt like it mostly invalidated the queer character. Plus more sort of pedophilia (bit of an immortal born pretty yesterday trope, with specific mention of looking underage) that felt unnecessary here too. Meh. 
What I think was supposed to be a magic addiction analogy never quite got there for me with how it paired with alcoholism.