Author Ilona Andrews highley recommended this book on her blog and I have to agree. It starts out a little slow, but once all the characters were introduced I was hooked. I quickly read through it. I couldn't wait to find out what happened. 
 The book is about Lucian, who has held guilt for is actions against his love, Rachel, sixteen years before in order to save his twin's life. What he has come to learn over the years is that his twin sister, Catarina's, life was more corrupt than he realized. She made a deal with a powerful demon in order to gain power when the war between the Fallen (yes those Fallen from heaven) and the Citadel (where the good people of faith reside). 
 The world structure is a lot to take in. The story is set in an alternate universe called the Woerld. It is a different plane of existence adjacent to Earth. Earth and the Woerld are bookended on either side by Heaven and Hell. Frohock does a wonderful job creating a truly unique world from any that I've read before. She does a great job of relaying to the reader the intricaces of the world without seeming to textbook about it. There are things that are told outright and things that we learn by actions. 
 The way that the story goes really sets up for other books in the series. I really hope that we get more. I am eager to find out where our characters go from here. Until Then!