For the sake of the environment, hardcovers are increasingly being shipped without plastic foil. A small label with the hashtag “#ohnefolie” shows you that it is a new product by sealing the open side of the cover in an environmentally friendly way.
Cut the seal in the middle and slowly peel or stick it to the inside of the cover from there, one after the other, on both sides.
First on the back of the book and then on the front.
If glue does remain, it can be easily removed with a drop of washing-up liquid.