Cat is an assistant to an architect in an alternate medieval Europe. A world where the sun is worshipped, and moon worshipers are feared and othered, confined to a specific quarter in the city despite both religions clearly worshipping the same god but through different means, a clear symbolism of the medieval Jewish population. While inspecting the scaffolding, Cat witnesses a murder, and so begins the hunt for a serial killer reminiscent of Jack the Ripper.

I loved everything about this book, it so perfectly blended my historical interests its like it was written for me. As Cat helps with the investigation, she becomes closely embroiled with the powerful ducal family that runs the town. Particularly their distant cousin, the Venatre (inspector) Simon who is in charge of finding the murderer. As is par for course for a young adult novel, Cat and Simon quickly develop feelings for each other, and dance around it for the entire novel. This of course leads to amazing angst moments when Simon thinks he almost lost Cat and has to reevaluate if he wants to stay away from her or not.

The reason Simon debates staying away from Cat is due mostly to his fear he will develop the same mental disorder his father suffered from, and which he daily helps his cousin Julianne manage. The kind hand schizophrenia and mental health was handled with in this novel, with its extensive author's note at the end, was such a necessity in this world which constantly villainies these disorders. But Beaty handles, particularly Julianne, with respect and dignity and reality. It was nice to see in a novel, especially in a YA novel.

As for the magic system in the book, that was so well done at first, but the more details we got about how they use magic and the abilities they have started to get confusing. It almost would be better with less detail about the magic, and instead leave it with just Cat's ability. The more detailed functionality of the stones and moonlight just convoluted what the magic was capable of. I kept zoning out and rewinding, then realized it wasn't important to really any aspect of the story and just let it go. Though aesthetically I love the idea of the moon worshippers having an entire magic system, I just think it would have been served better left in more mystery.