Showing Deliver Us from Evil by Tom Holland

Wiltshire, during the dying days of Oliver Cromwell's Republic. Robert Vaughan is the son of a Parliamentarian officer who is investigating a series of grisly murders which suggest a link with Satanic rituals at Stonehenge. The return of a notoriously wicked Cavalier, signalling the impending royalist restoration, leads to a terrible tragedy for the Vaughans. Robert's flight from his violent, terrifying past leads him to Restoration London, where he works as scribe for Milton, and where he survives the Plague and the Great Fire.

But Robert is led along a dark path, to vampirism and beyond, as he devotes himself to gaining the powers that will enable him to fight an evil killer of seemingly satanic powers. He will travel the globe, from the ancient ghetto of Prague to the virgin forest of the New World, as he aims to gain revenge on those who betrayed him.