I would also say the behavior of characters in this novel is very human and thus relatable. They lie, betray, make mistakes, act on impulse, pursue their selfish agendas, doubt themselves - Violet's actions and motives made sense to me. I am getting a bit sick of publishers describing characters as "morally grey". In this particular novel, I would describe Violet as just very human and honest with herself. Yes, she is cynical and jaded, but given her position in life, where she came from and who she serves, it is not a surprise. It is actually very logical.
Anyway, my final point on this book is that it is a fairy tale retelling of sorts. You do not need to know which one. Just go into it blind. If you like fairy tales, forbidden romance and dark magic, do not pass this one by. It is surprisingly fresh, well-written and unpredictable. 5 out of 5 stars from me.