Those Who Hunt the Night by Barbara Hambly

Someone is killing the vampires of London, England by exposing them to sunlight while they rest and then draining their blood. Simon Ysibro, who has been a vampire since before the Renaissance, wants to know who is responsible for these murders. Because he and his cohorts must avoid daylight, he seeks the assistance of James Asher, former agent for the British government, currently an Oxford professor. To Asher, the vampires are monsters, and deserve their fate. But Asher agrees to search for the murderer, since Ysibro has threatened to harm his wife if he refuses.

Hambly successfully creates an eery1907 London and Paris with flickering gaslight, swirling fog, and shadowy characters. Her vampires are indeed murderers - not exactly the type you'd want to invite to dinner. But they are not card-board characters - Ysibro especially, exibits a certain faded old-world charm and noblesse oblige. Nor are the humans two-dimensional. As a government agent, Asher has committed acts which make him wonder if he is any better than the vampires. A word about Asher's wife Lydia - she is a brave, intelligent woman who is willing to take things into her own hands. For those who can't stomach Bella, from the Twilight series, she comes as a welcome changes.

A good book for teens who enjoy the vampire genre.