The Rosetti siblings, Christina, Dante (Gabriel), Maria, and William, are haunted by the vampire who was once their uncle, John Polidori. The vampires possessively love certain humans and grant those humans great powers of creativity. Christina both loves her uncle and yearns to be free of him. The other humans who receive the attentions of the vampires likewise feel both a forbidden attraction and a horrified repulsion at their own potential damnation.
Tim Powers is known for his “secret histories”, wherein he takes historical events and figures and supplies occult and fantastical explanations for what occurred.