I am still liking that Victoria, while a venator (vampire slayer), is still only twenty years old, and her choices seem age-appropriate to me. Also, we can see her growing and learning.
I thought Sebastian's arc would culminate in his becoming a venator, but I was wrong; it's revealed that he is one, but he doesn't practice, until events at the end of book three push him back into it. So now I'm wondering what the end of his arc is again; this is a good thing, as there are still two books to go! I like the relationship between him and Victoria, which to me seems to be purely sex for her but sex plus a little more for him. It's contrasted with her brief dalliance with the venator Zavier--he wants romance, and she cannot give it to him. She's still hung up on her dead husband, I believe, and also learning about her own sexuality. Both Zavier and Sebastian are part of that process.
As soon as we learn Max the powerful venator was once a member of the Tutela, who provide blood for the vampires, and had betrayed his father and sister to be eaten, I thought, "Snape!" This impression was not helped by his messy black hair and always wearing black. Or by him having to kill his friend and mentor at her request for the good of all. This isn't a bad thing. I like Snape a lot. It just made me laugh. Also, for the romance reader there were a raft of clues that Victoria is romantically inclined towards him though she is oblivious to it until they kiss, and even afterwards is somewhat in denial. The events in these two books reinforces my opinion that Victoria will end up with Max.
By book three, Victoria is in charge of the venators after her Aunt Eustacia sacrifices herself; I'll be interested to see how that plays out over the next two books.