Boxes always give away that you own undecorative things. This box is different. All you can see are books.
How I did
I used a wine box, but I am sure that any box will be good, as long as the books that you are using are close to aligning the edge, and as long as it fits in the debts of your bookshelf.
This one was to big for my bookshelf, so I had to shorten it.
The books should be a little big higher than the box.
I cut the back of the books out. The back alone was too thin for this purpose, because I would grab the edge and pull the box out of my bookshelf. Therefore I cut about ½ cm. from the back all the way through the books.
It ended up like this:
I shortened some of the books at the bottom:
I then glued the back on the box. I used glue from the DIY store, it was called mounting adhesive. I then put something heavy on top.
The box was finished after one night of drying.