The idea is from the Californian design studio Able + Baker and it's called The Modern Library Storage Bin. Of course we cannot say that the name is not descriptive, nor adequate for what it really is: a useful hidden storage box behind book spines used.
But do not believe, the thing has more substance than it seems at first glance. Actually, although it could fit in any bookcase, the size of the plywood box is specially sized for Ikea Expedit shelves. Each unit is different and the books to be used are carefully chosen to form a harmonious and balanced composition, which you can also order personalized if you wish.
Of course, if you don't want to buy it, you can also consider the option of do it yourself. The box is simple, because you can use for example the plastic Lekman model of Ikea or any other that you have at home, but then you will have the most complicated task, cut the spines of the books, for which you will need a very sharp cutter , patience and good pulse. You dare?