I'm a fan of the E.E. Knight Vampire Earth series currently on the 6th book in the series.
"In the Vampire Earth series, aliens from a world known as Kur have taken over the world, destroying human society and enslaving the survivors. The novels follow the life of David Valentine, a young man who enlists with Southern Command, one of the few remnants of the old U.S. government scattered around, as he follows his heart even when it conflicts with orders."
Quick summary from the wiki page.