This book was super engaging, I finished it in a couple of hours just reading nonstop. The mystery was one that you couldn't really solve on your own, I never suspected the perpetrator until the last 15% of the book where they spell it out for you. I feel like that's pretty common in this series but I find it more fun when I can at least try to guess. 

Hero and Sebastian are very cool as usual, lots of neat and depressing historical info, and some good insight into some side characters. 

I do wish the folklore aspect had either been explored more or not included at all. It felt underwhelming how little it played into the plot itself considering how neat all the info was.