I finished this book a few weeks back and have had some time to digest it. I have read pro and con reviews of the book on good reads and other sites. The main issue most negative reviews seem to have is a flat nature to the characters. I personally marked this book 4 stars on Amazon and stated that I was thankful that J.Butcher skipped doing a full book of character backstories and development.
So, who do you think the main protagonist is? The "enemy" is purposefully unclear, but I find that I am unsure who the main character is. I can't really think of a successful book or series of books that does not boil down to 1 good (entity) vs 1 bad (entity).
*example* The Bible : God/Devil(human nature). The lord of the rings Bilbo, Soramon(sp). The Wheel of time: Richard vs many diff evil main chars.

A good summary of "In Jim we trust."