Back cover
Also called fourth cover, outside back cover
The back face of the cover. It carries the blurb, the barcode, the price and often the publisher’s logo; the front cover is the first.
In practice
It is the side a reader turns over in a bookshop, and the one where the technical constraints gather. Reserve the barcode’s space before laying out the text, on a light background, clear of the flaps and the spine. If the cover is laminated or varnished, check on the proof that nothing hinders the barcode.