Price of Passion by Cassandra Pierce

In Victorian Oxford, Professor Algernon Price strikes a scandalous bargain with a young man who offers companionship in exchange for meals and a place to stay. He soon discovers, however, that his guest prefers meals consisting of human blood and a room that blocks all traces of sunlight. But even that is not as shocking as the emotions that arise between them, or the hope that his strange guest might be the one to alleviate his loneliness.