If offered the chance--by cloak, spell or superpower--to be invisible, who wouldn't want to give it a try? We are drawn to the idea of stealthy voyeurism and the ability to conceal our own acts, but as desirable as it may seem, invisibility is also dangerous. It is not just an optical phenomenon, but a condition full of ethical questions. As esteemed science writer Philip Ball reveals in this book, the story of invisibility is not so much a matter of how it might be achieved but of why we want it and what we would do with it.