Captive — Piers Anthony

Dane at 18 is a rich young man, the likely heir of a highly successful company CEO. He is abducted and held for ransom by Clare, 25, a lovely former prostitute. Bored in a hot cabin without electricity they strip for comfort. One thing leads to another, and they discover that they both have a similar secret sexual problem. They can get it on to climax, but only with each other; this is an intensely sexual relationship. He quickly falls for her; then she falls for him. When he is rescued, he progresses from being her captive to her captor. Then the real story begins. He gives his folks an ultimatum: get Clare free and let him marry her, or he will never get into the family business. So instead of paying ransom, they must welcome Clare into the family. Dane's dad is not a man to cross, but when he faces off with Clare the two discover mutual respect and he wins her loyalty. Just as Clare shares a sexual secret with Dane, she shares a power of personality with Dane's father.