How can I cover books with contact paper without bubbles? I have to cover some books with adhesive contact paper. Although I try to do it slowly and with the help of a ruler, I systematically get some bubbles between the book and the cover.

Is there a good trick to do that properly?
Try removing the paper off the plastic foil during the process, not before like removing a little bit of foil, sticking it on the edge, then pulling away the paper flat on the book.