Device for forming a folding area (6, 6') lying adjacent to both sides respectively of a spine area of outstretched book covers or a spine area and a folding area (6, 6') located on both sides respectively of the spine area of outstretched book covers corresponding to the shape of the back of a book block later on forming a book together with the book cover, with at least a first forming tool (8, 8') for a book cover belonging to a block with a straight spine and with at least a second forming tool (10, 10') producing a rounding of the spine area of the book cover for a book cover belonging to a block with a round spine, with an operating position for one of the forming tools (8, 8', 10, 10') and with in each case an idle position for the one or the other forming tools (8, 8', 10, 10'), with a counter tool aligned to an outer face of the spine area of the book cover, which has two counterblock mouldings (20, 20') arranged at a distance from each other and are laterally adjustable corresponding to the width of the spine area of the book cover, in which the forming tool (8, 8', 10, 10') is arranged in its operating position directed to an inner face of the spine area of a book cover lifting the spine area of the book cover between the two counterblock mouldings (20, 20') and in so doing forming a back ridge of the book cover, with in each case a tool beam locked by power or force-fit with the forming tools (8, 8', 10, 10'), with a pick-up element for the tool beam of the forming tool (8, 8', 10, 10') arranged in the operating position, characterised in that the device has a single actuating drive for the forming tool (8, 8', 10, 10') arranged in each case in the operating position, the tool beam of the forming tool (8, 8', 10, 10') arranged in each case in the operating position is designed to be coupleable with the single actuating drive, and each forming tool (8, 8', 10, 10') has two laterally adjustable shaping strips (11, 11', 22, 22') spaced apart from each other, which are respectively designed to be concertedly adjustable, altering their mutual distance. with at least a first forming tool (8, 8') for a book cover belonging to a block with a straight spine and with at least a second forming tool (10, 10') producing a rounding of the spine area of the book cover for a book cover belonging to a block with a round spine, with an operating position for one of the forming tools (8, 8', 10, 10') and with in each case an idle position for the one or the other forming tools (8, 8', 10, 10'), with a counter tool aligned to an outer face of the spine area of the book cover, which has two counterblock mouldings (20, 20') arranged at a distance from each other and are laterally adjustable corresponding to the width of the spine area of the book cover, in which the forming tool (8, 8', 10, 10') is arranged in its operating position directed to an inner face of the spine area of a book cover lifting the spine area of the book cover between the two counterblock mouldings (20, 20') and in so doing forming a back ridge of the book cover, with in each case a tool beam locked by power or force-fit with the forming tools (8, 8', 10, 10'), with a pick-up element for the tool beam of the forming tool (8, 8', 10, 10') arranged in the operating position, the device has a single actuating drive for the forming tool (8, 8', 10, 10') arranged in each case in the operating position, the tool beam of the forming tool (8, 8', 10, 10') arranged in each case in the operating position is designed to be coupleable with the single actuating drive, and each forming tool (8, 8', 10, 10') has two laterally adjustable shaping strips (11, 11', 22, 22') spaced apart from each other, which are respectively designed to be concertedly adjustable, altering their mutual distance.