At the start of this book I found it difficult to sympathize or like Aislinn. What she wants and needs is more important then what the other characters want and need. And she chooses to remain willfully ignorant about the powers of Fairie. No she isn't educated, but she doesn't ask to be either.
However it is that selfishness and impulsivness, the living in the moment that makes her the Summer Queen. In fact you could question whether she is the Summer Queen because she has those qualities or if she developed them as she became the Summer Queen.
I love how this book emphasizes the changes Fairie has on mortals. It wasn't something you could really see in the other books as they focused on one mortal influenced by one court. In this book Seth is has interaction with three courts, and you can see the minor changes each court brings out in him.
I think what I really love about these books though is the real sense that these are gods. Melissa Marr imbues the books and characters with a sense of timelessness and power, and so really conveys that fact. These are not simple fairies, but powerful gods with whom it is dangerous for mortals to congress.