Lucifer's War. The Carolingian, #1

Since the first moment that humans left the trees and began to walk upright, a secret war has been fought. On one side of this ancient battle are the Old Ones, malign entities that feed on the suffering of humankind. Their weapon? Magic and religious fanaticism. The only force able to hold them back is the ancient order of the Lumina. Dedicated to the liberation of the human spirit, they employ reason, understanding and technology to stop the superstitious rampages of the Old Ones.
When Officer Richard Oort of the Albuquerque Police Department rescues a mysterious teenage girl from a trio of inhuman hunters, he's hurled into the crush of this primal battle. Recruited by the Lumina to serve as their newest paladin, Richard joins a handful of unlikely allies, including an adolescent sorceress, an enigmatic billionaire, a sexy coroner, and a wandering god with multiple personalities.
And then there's Richard's boss. Damon Weber is a handsome, intelligent, and honorable man and Richard falls hard for him. Even knowing his feelings will never be reciprocated. The Old Ones and their righteously intolerant pawns seek to destroy Richard - or subvert him to their cause - ruthlessly expending all the powers of magic and organized religion at their disposal. As the gates between the universes shred apart, it may be up to Richard to save humanity from the endless horror of the next Dark Age.