The Moustache by Emmanuel Carrère

One morning, a man shaves off his long-worn moustache, hoping to amuse his wife and friends. But when nobody notices, or pretends not to have noticed, what started out as a simple trick turns to terror. As doubt and denial bristle, and every aspect of his life threatens to topple into madness - a disturbing solution comes into view, taking us on a dramatic flight across the world.