Cover applier for providing book covers (5, 5') for a production unit of a book production line with • a first receiving device for book covers of one format respectively that may be placed individually, shingled and/or as a stack, • a lateral adjustable centring device arranged on the first receiving device for applying the book covers that may be placed individually, shingled and/or as a stack in a defined lateral way according to the centring necessary for the production unit of the book production line. • a cover stack arranged downstream of the first receiving device with a stacking shaft and a first separating device for removing the lowest book cover respectively from the stacking shaft as well as for providing the book cover removed for the production unit of the book production line and • a transporting device of the first receiving device for transporting the book covers placed individually, shingled and/or as a stack from the first receiving device into the stacking shaft of the cover stack arranged downstream, characterised in that • a second receiving device for a stack of book covers of different formats is arranged upstream of the first receiving device, • the second receiving device has a second separating device for removing the lowest book cover respectively from the stack of book covers of different formats lying on the second receiving device and forwarding the book cover removed to the first receiving device in a transporting direction, • the cover applier (9, 9') has a control, to which information regarding the format and sequence of the book covers in the stack of book covers of different formats is transferable, • the centring device is connected to the control of the cover applier (9, 9') and is made lateral adjustable for moving and/or aligning a book cover removed from the second receiving device and located on the first receiving device respectively in a defined lateral way according to the information regarding the format and sequence of the book covers in the stack of book covers of different formats and according to the centring necessary for the production unit of the book production line. • a first receiving device for book covers of one format respectively that may be placed individually, shingled and/or as a stack, • a lateral adjustable centring device arranged on the first receiving device for applying the book covers that may be placed individually, shingled and/or as a stack in a defined lateral way according to the centring necessary for the production unit of the book production line. • a cover stack arranged downstream of the first receiving device with a stacking shaft and a first separating device for removing the lowest book cover respectively from the stacking shaft as well as for providing the book cover removed for the production unit of the book production line and • a transporting device of the first receiving device for transporting the book covers placed individually, shingled and/or as a stack from the first receiving device into the stacking shaft of the cover stack arranged downstream, characterised in that • a second receiving device for a stack of book covers of different formats is arranged upstream of the first receiving device, • the second receiving device has a second separating device for removing the lowest book cover respectively from the stack of book covers of different formats lying on the second receiving device and forwarding the book cover removed to the first receiving device in a transporting direction, • the cover applier (9, 9') has a control, to which information regarding the format and sequence of the book covers in the stack of book covers of different formats is transferable, • the centring device is connected to the control of the cover applier (9, 9') and is made lateral adjustable for moving and/or aligning a book cover removed from the second receiving device and located on the first receiving device respectively in a defined lateral way according to the information regarding the format and sequence of the book covers in the stack of book covers of different formats and according to the centring necessary for the production unit of the book production line.