The invention relates to a device for deforming lying outstretched book covers with deformation tools for a back region and for a respective rebate region of the book covers. At least one first and at least one second deformation tool are arranged for a book cover belonging to a book block with a straight or with a round back. The device has in each case one of the deformation tools positively or positively connected to the tool bar. In addition, the device has a single actuator, with which the tool bar of each in the working position arranged deformation tool is formed coupled. Finally, each deformation tool has two spaced-apart, laterally adjustable moldings, which are each designed to be adjustable, changing their mutual distance.