The Devil on Horseback — Victoria Holt

From the moment that beautiful eighteen-year-old Minella Maddox saw Charles-Augueste, the haughty, arrogant Comte Fontaine Delibes, his satanic looks thrilled her with a sense of danger and excitement.
A French aristocrat of wealth and power, the Comte had a reputation for taking what he wanted, expecially women. And right now he wanted Minella. She was the most desirable thing he had ever seen. Minella was the woman he would marry, and nothing would be allowed to stand in his way...not even his wife.