If you've ever been told you're too sensitive or too much in your head, or spent years trying to be more outgoing and more the kind of person the room seems to want, you'll recognise something in Susan Cain's work before you've finished the first chapter. Her 2012 book Quiet: The Power of Introverts in a World That Can't Stop Talking made a case that feels obvious once you hear it, and yet clearly needed saying: that somewhere between a third and a half of the population is w