"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):
John R. Levine
UNIX For Dummies has been the standard for beginning UNIX references for nearly ten years, and this latest edition continues that tradition of success. This unparalled resource is updated to cover the latest applications of UNIX technology, including Linux and Mac desktops as well as how UNIX works with Microsoft server software
Thorough coverage of how to handle:
ther basic tasks
A great guide for the first-time UNIX desktop user growing accustomed to the ins and outs of the OS, as well as the beginning administrators who needs to get a handle on UNIX networking basics.