These flexible bookshelves, called “Chuck” (site in German) flexes to fit whatever books or other items you place on them. The shelves are made of a a series of pliable wooden planks all coming together at the two ends inside a metal bracket. It almost looks like a mouth. The bracket has rods going through slots in the wood to keep them from sliding right out.
The shape changes depending upon what size books you place in the shelves and where you place them. Here’s a video showing a man rearranging the shelves a few times.
The website is in German and I don’t really see a way to purchase them (probably since I don’t speak German). Natascha Harra-Frischkorn designed the shelves.