'Excuse me, I loved that book' ... commuters reading. Photograph: Dan Chung
"Don't talk to strangers," parents sternly warn their children. But as Terry Teachout's blog details, some books can cut through all such social precepts and banish our stiff upper lip. He tells of purchasing a couple of Elmore Leonard paperbacks only to be stopped by the cashier exclaiming how much he loved the author, and when, sitting in the restaurant of a hotel in Washington DC, a businessman stopped to tell him how much he was going to love reading Unknown Man #89.

It reminded me of being slumped in the doctor's surgery a while ago, a wretched shadow of a human being, the world bleached of all happiness. I could not think of a single thing I loved as I breathed in the horrid smell of disinfectant and regarded the utter ghastliness of the flesh-and-blood self when ill. This was life, when it was too poorly to think about art. And then I looked up and a bright spot of colour made my heart leap - the paperback of Case Histories by Kate Atkinson nestling in another patient's hands. The memory of reading it late into the night immediately sucked away my illness. "Do you like it?" I had to yelp out loud. "You must finish reading it . . . have you got to the bit yet when ... what do you think about the character who..." I had soon made a little connection there in the grim room, despite having given away the plot.

This instinct, in even the most reserved of human beings, to stop strangers when they spy one of their most beloved books can even transcend language barriers. As I routed through the dust and flies of a secondhand bookshop in New Delhi, the shopkeeper began wildly gesticulating at the dog-eared copy of Great Expectations in my hand. Then there was the long, hot summer after my A-levels, when I was sprawled in Retiro park, Madrid with a copy of The Waves by Virginia Woolf, and a boy approached to share with me how it had changed his perception of life.

Have you ever been stopped mid-sentence while reading a book - whether on the tube, in a plane or a park - by a stranger? And what books do you think illicit such instinctive praise from the public?