I loved this book, it totally blew me away. Started off strong because it began in Lexington, soft-spot for my hometown.
I liked Luke from the beginning, the humans on the other hand took a bit of warming up. Callie and Lukes banter was very well done, I found myself laughing out loud several times. 
Hands down the best part was when they traveled to Hell. Meeting the Demons, Lucifer and Lillith; I was on edge the entire time and couldn't put the book down.