Rowan. The Hampshire Vampires, #3

Thérèse. An ancient lustful evil made flesh in the shape of a flame-haired seductress. A vampire who feeds on men and their desires. She's taken the mortality of many a victim, but only once has she unknowingly taken a heart as well. Rowan Selkirk lost his to this beautiful creature along with his soul-he loves her in spite of what she is. Wandering in his eternal darkness, Rowan meets Marcus Camberley across the green baize of a London gaming table and finds himself attracted to the secrets he sees in the other man's eyes.
A friendship is born from nights of passion and together they find their way south, where others of Rowan's kind await his coming, others determined to destroy the evil that is Thérèse. Their plan will extract a high price however-from Rowan most of all. He must find the strength to put aside his love and his friendship if he is to save them. The darkness around them deepens as they learn some shocking truths-truths that illuminate the real and terrible shadows of Thérèse...