This study presents the metaphoric usage of conscience as a book from its beginnings in the Christian late antiquity to its decline in the 18^th century. It was commonly believed that everything a human had ever done, said or thought was recorded in this Book. At first, the Book of Conscience was exclusively depicted as a testimonial at the Last Judgement and therefore associated with the Book of Life. In parallel to the conceptual development of independent conscience in the High Middle Ages, the belief became prevalent that a look in one's own Book of Conscience even in earthly life was not only possible but mandatory. This obligation was soon accompanied by the idea that the look into the Book of Conscience not only served the perusal and therefore self-awareness, but also the rectification of the read and thus self-perfection. The own biography became the object of consistent reflection. In this study, sermons, religious writs of admonishment, theological treatises, diaries, hymns, and multiple other genres of text are taken into account. In its entirety, it allows a multi-faceted view on the developments of the metaphoric depiction of the Book of Conscience from its first emergence until its eventual disappearance.