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. In this lively look at a timeless idea, Ball provides the first comprehensive history of our fascination with the unseen. This sweeping narrative moves from medieval spell books to the latest nanotechnology, from fairy tales to telecommunications, from camouflage to ghosts to the dawn of nuclear physics and the discovery of dark energy.  Along the way, Invisible tells little-known stories about medieval priests who blamed their misdeeds on spirits; the Cock Lane ghost, which intrigued both Samuel Johnson and Charles Dickens; the attempts by Victorian scientist William Crookes to detect forces using tiny windmills; novelist Edward Bulwer-Lytton's belief that he was unseen when in his dressing gown; and military efforts to enlist magicians to hide tanks and ships during WWII.  Bringing in such voices as Plato and Shakespeare, Ball provides not only a scientific history but a cultural one--showing how our simultaneous desire for and suspicion of the invisible has fueled invention and the imagination for centuries. In this unusual and clever book, Ball shows that our fantasies about being unseen--and seeing the unseen--reveal surprising truths about who we are.