The Structure of Men and Women
They are very different. What they really like about each other is something that they don't have themselves. Their unity is based on their contradictions. That's why they don't get each other. They have different biological tasks, different desires and goals. Their only things in common are children and mutual interest. Yes, they need each other. Their relationship is a symbiosis, they are halves taken singularly and only after finding each other they become one whole thing.
The book helps to answer the question who is who. It helps to have a look into your own soul as well as into the souls of those close to you. And it helps to understand the nature of human relationships.