Carpe Jugulum by Terry Pratchett

Mightily Oats has not picked a good time to be priest. He thought he was there for a simple little religious ceremony. Now he’s caught up in a war between vampires and witches, and he’s not sure there is a right side. There’s the witches — Agnes, Magrat, Nanny Ogg, and the formidable Granny Weatherwax… And the vampires: the stakes are high but they’re intelligent — not easily got rid of with a garlic enema or going to the window and saying “I don’t know about you, but isn’t it a bit stuffy in here?” They’ve got style and fancy waistcoats. They’re out of the casket and want a bite of the future.