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?
I have never personally done this with books but in concept there are a few things you need to keep in mind that will help make this process easier.
Remove all debris from the cover of the book. Dust particles and hair will make this a near impossible process. Small particles that you cant see and wont show up until you make contact. This is something you likely are already mindful of but you need to be sure of your cleaning medium as well. Something with paper fibers like Kleenex or paper towels would leave behind stuff as well. Dust in the air as well won't be helping this so need to pick a good location
Your surface needs to be flat. I mean this both as your working surface and the book itself. You might be having an issue if you are working the adhesive sheet from the top to the bottom of the book. The binding would make the book sit not perfectly flat. You might have more luck moving from left to right or more accurately start at the binding and work away from it. Working from top to bottom might cause the book pages to slide as you progress.
Besides the ideas given in other answers I found two tricks to make the process easier:
My procedure as learned from a librarian (those books are covered with a thicker kind to make them last longer, but it also works with the thinner kind):
Move the book, not the foil.
Mark and cut the foil to the required size. Gently fold and mark the center line with a small cut, this will leave the foil with a small notch, unlike markings on the paper. (Alternatively, waterproof pen on the foil should work too, but needs more equipment, you have the scissors out anyway.)
Place the foil paper-side up on the table and gently pull off the backing on the side away from you until slightly beyond the central line - basically enough for one side plus the spine plus a small margin.
Gently place the spine of the book along the center (use the notches for alignment). For thin books, just put it on, for wider spines, start at one vertical side and gently roll it onto the foil, using the curve of the back. (Paperbacks sometimes are curved inwards, in that case, use the process for the front & back cover as described below.)
Then tilt the book slightly away from you and use it to pull the whole setup towards the edge of your table. Then guide the book down along the edge, so that the table edge works like a straight edge. As the foil remains flat on the table (and usually there’s also a bit of static helping it cling to the table), there’s very little risk of air bubbles forming.
Finish the edges of this side (cut and fold as needed) first, then turn the book around so that you can repeat the process for the other side.