"What is the book that changed your life? (not novels or religious texts)"
I think it's a wonderful way to connect in a less superficial way and learn a little more about each other. It's also a wonderful way to discover new books worth reading.
This is one of them:
Foster W. Cline
This parenting book shows you how to raise self-confident, motivated children who are ready for the real world. Learn how to parent effectively while teaching your children responsibility and growing their character. Establish healthy control through easy-to-implement steps without anger, threats, nagging, or power struggles. Indexed for easy reference.