Hammer Commission - Book #1
Mark's job seems pretty dull, working as an investigator into crimes committed against Church property, theft of holy objects, vandalism; nothing terribly exciting but he does get to travel the world.
That's just the window dressing. Mark does work for the Church, but as an elite member of a thousand year old secret society that hunts down devils, demons, and other evils. His job is not just to find them, but to remove, dispel, or kill them: he's on the front lines of the secret ongoing war between Heaven and Hell. However as wars go, it has been a fairly easy one for the last few decades, with nothing seriously evil having been summoned since the last world war.