This novel is the third book of the Grimnoir Chronicles trilogy, and I'm going to have to say that I will definitely be looking for the first two books, as well as any other books by this author. Larry Correia has a lyrical quality to his writing, which supports the setting in an alternate world United States. Set primarily in the equivalent of the 1930's, the story follows a group of people attempting to save the world from an extra planar entity bent on devouring the energy of the magic using people of the world. The "physics" of magic in this novel is intriguing and believable, establishing a strong underpinning to the framework of the action throughout the story.
This is a story I would recommend to anyone slightly interested in fantasy novels. The characters are likeable and draw the reader into the story, to the point that the climax of the story is engrossing enough to give the reader cause to lose sleep until after the book is finished. Personally, I'm going to look for more of Mr. Correia's work, he seems to be an author I will avidly follow.