Rawblood by Catriona Ward

She comes in the night. She looks into your eyes. One by one, she has taken us all. For generations they have died young. Now Iris and her father are the last of the Villarca line. Their disease confines them to a lonely mansion on Dartmoor; their disease means they must die alone. But Iris breaks her promise to hide from the world. She dares to fall in love. And only then do they understand the true horror of the Villarca curse.