"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):
Clinton Ober, Stephen T. Sinatra, Martin Zucker
Earthing' introduces readers to the landmark discovery that living in contact with the Earth's natural surface charge - being grounded - naturally discharges and prevents chronic inflammation in the body. This effect has massive health implications because of the well-established link between chronic inflammation and all chronic diseases, including the diseases of ageing and the ageing process itself.