Case binding.

Case binding makes the cover as its own object, boards and spine and covering material assembled away from the book, and attaches it by pasting the text block's endpapers to the inside of the boards (Etherington and Roberts, case binding). That separation is what makes it a production method rather than a craft, because cases can be run ahead in quantity while the blocks are still being printed. Case wrap is the print-on-demand form of the covering, where the printed cover itself is laminated and folded around the boards instead of cloth carrying a jacket; Lulu sells it as casewrap with a glossy or matte finish and a stiff cover board (Lulu), and KDP's hardcover file carries a 0.51 inch wrap that folds around the case board plus a 0.4 inch hinge gap so the book can open (KDP hardcover cover specification). The cost sits in the case, not the paper: on Amazon.com a black-ink hardcover carries a $5.65 fixed cost (KDP hardcover printing cost) against $1.00 for the same paperback, on the same $0.012 per page (KDP paperback printing cost). That gap decides whether a hardcover edition is worth listing at all, and it is also why KDP stops hardcovers at 550 pages where the paperback runs to 828.