"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):
Two Books for the Price of One––both an interactive reference & tutorial! C++ In Plain English, 3rd Edition, gives instant access to the C++ language through a detailed reference section of key C++ components and a dense tutorial that describes the essentials of C++ programming. Extensive cross–references with live page numbers make this is the perfect book to prop next to your computer while programming in C++.