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The Vampire Viscount US DE
by Karen Harbaugh (Signet 1995).
Nicholas, Viscount St. Vire finds that the eternal youth and the supernatural strength of a vampire means little in the face of impending insanity and the eventual deterioration of his senses. Only the willing embrace of a virginal young woman can reverse his condition. Who better for his wife-to-be than the impoverished Leonore Farleigh, whose abusive father sells her to St. Vire to pay off gaming debts? Leonore agrees to marry him--how else is she going to save her sister and her mother from their poverty and pain? But she soon finds she's stepped into a marriage of inconvenience… and possible death.