The 23rd Discworld novel.
Mightily Oats has not picked a good time to be a priest.  He thought he'd come to Lancre for a simple ceremony.  Now he's caught up in a war between vampires and witches.  There's Young Agnes, who is really in two minds about everything.  Magrat, who is trying to combine witchcraft and nappies, Nanny Ogg . . . and Granny Weatherwax, who is big trouble.
And the vampires are intelligent.  They've got style and fancy waistcoats.  They're out of the casket, and want a bite of the future.  Mightily Oats knows he has a prayer, but he wishes he had an axe.