This movie is based on a book????

I remember reading an article about an unproduced screenplay about two souls that meet in heaven, then are born, then have to find each other on earth. It was based on a much loved novel written by a woman, and the screenplay became a legendary unproduced project that kept getting close to production. They emntion that "Made In Heaven" borrowed a little from the concept. Does anyone know the book I'm talking about? It had a title like "Forever" or "Always"