What happens when Tertuliano M-ximo Afonso, a 38-year-old professor of history, discovers that there is a man living in the same city who is identical to him on every physical detail, but not related by blood at all. And what happens when each of these men attempt to investigate each other's lives? How do we know who we are? What do we mean by identity? What defines us as individual, unique people? Could we ever come to terms with the existence of another person with our voice, our features, our everything, down to the smallest distinguishing mark? Could we change places with our double without those closest to us noticing? Dark yet comic, Jos - Saramago's new novel can be read as an existential thriller, but it is above all a work of literature that immerses us in the essential questions of life. It is certain to become a 21st-century classic.