From Fields of Gold — Alexandra Ripley

The war has swept away all her wealth. Now poor, nearly thirty, and without a husband, Francesca "Chess" Standish has only her pride, a crumbling Tidewater mansion, and a patent on a machine that needs the right man to fulfill its promise. Barely twenty and outrageously handsome, Nate Richardson is that man. With a heart committed to another man's wife and a raging ambition to be rich, he agrees to marry Chess. lie gets the patent. She gets a business partner and, she hopes, a husband who will someday want her. But the bargain will plunge her into a world of betrayals, cutthroat deals, and raw passions. And it will transform Chess into a woman to be reckoned with--unpredictable, newly glamorous, and strong enough to fight any rival, even the world, for her right to love.