If you've ever had the "who would win in a fight?" argument*— and enjoyed it— you might also enjoy this novel. It begins with an interesting alternate history concept: would the outcome of WWII have been the same if the Nazis had actually succeeded in creating their master race? What if the British had used warlocks to combat this new threat?
Sure, the plot may not progress very quickly in some places, and you might end up hating all the characters just a little, but facts and fantasy blended seamlessly enough for me to see the charm in both the detail and pragmatism with which Tregillis has infused his book. There are also Lovecraftian monster/demon creatures that exist in the spaces between time and want all of humanity dead, which is clearly awesome in both senses of the word.
*I'm a Batman girl, but it's always Superman, hands down. (Or Doc Manhattan, if we're traversing DC universes.)