"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 (the full list is here):
This foundation guide to Windows programming covers the enhancements of Windows 3.1. These include the new Dynamic Data Exchange (DDE) protocol, the printing and TrueType font application programming interface (API) and more. As useful to owners of the current edition as the new Windows programmers, this book is packed with explanations, insights, tried and tested programming techniques and scores of sample programs written in C.