Went into this book knowing nothing, and sort of just sloughed through it through sheer force of will. A fair number of things kept this book from riveting itself to my hands: the lackluster introduction to this universe's version of magic, the switching POVs (which normally doesn't aggravate me, so I'm not sure what Enthoven did wrong), and, most of all, the fairly bland and annoying main characters (Jack and Charlie -- I'd mistake one for the other earlier on in reading the book. As for Esme, normally I adore badass chicks but she had zero in the way of a personality for me. No pass).
What saved this book from a miserable two stars (the second star added on mainly because only books I truly hate get just one star) was Hell. Hell was fascinating. Godfrey was excellent. Hell brought out the best in Jack -- his exasperation with all the shit happening to him was possibly only shining point in the entire book. The various demon gladiators were almost hilarious, and I soon became more interested in them than in either the main characters or the main villain, who came up pretty lackluster in comparison.
Basically Hell was brilliant, and Enthoven shouldn't have waited until the middle of the book to get there.