A doppelgänger is a biologically unrelated look-alike, or a double, of a living person. In fiction and mythology, a doppelgänger is often portrayed as a ghostly or paranormal phenomenon and usually seen as a harbinger of bad luck. Other traditions and stories equate a doppelgänger with an evil twin. This is exactly what a doppelganger is: your double, your mirror image in a world of strangers. Many cultures throughout the world believe that seeing your double brings nothing but bad luck, and for many historical figures, this was true. These figures include names such as Percy Bysshe Shelley, John Donne, Johan Wolfgang von Goethe, Emilie Sagee, Abraham Lincoln, George Tryon, Guy de Maupassant, Catherine the Great, Queen Elizabeth I, Maria de Jesus de Agreda, and Sir Frederick Carne Rasch. Another captivating notion closely related to that of the mysterious doppelganger phenomena includes the evil twin and the alter ego, all of which are elaborated on in this book. And, while in the old days, seeing your look-alike meant someone close to you would die, in this day and age, people are willingly becoming doppelganger detectives, all to find that special someone who is their spitting image. For some, it's all more than creepy, for others, it's just a question of visual similarity. In other words, you just look alike, you're not the same. Whatever you choose to believe, it is remarkable and even a little bit bizarre.