The Touchstone by Edith Wharton

Stephen Glennard is in desperate need of money; his career is in ruins and he wants to marry his beautiful fiancee. He unearths the passionate love-letters written to him by the famous, now-deceased author Margaret Aubyn, and sells them, erasing only his name. He makes a fortune from the betrayal and begins his marriage from it.The Touchstone was Edith Wharton's first published novella.