Taken By Desire - Tales Of The Demon Kin, #7

Novus Vita has been at war with the Demon Kin homeworld of Belleren for over a decade. Although they have formally surrendered, the Novus Vitans continue to struggle against their demonic conquerors. A Novus Vitan Angel, Promise knows the difference between right and wrong. Especially where the loathsome Demon Kin are concerned. Cain is a Demon Kin noble captured by the Novus Vitans and slated for use in the secret experimental facility Promise supervises.
He knows he should loathe Promise as much as she does him. Yet the instant attraction between angel and demon refuses to die. A scorching novel of sexual initiation.