As a conceptual design, this sleek curved bookcase looks ideal for storing things, sitting and reading. One has to wonder a bit about the lack of base and the potential for roll but weighted right and this bookcase design could be relatively believable. Better yet, what if it were designed somehow to roll on purpose?
Clearly the designer has thought carefully about assembly and allowed, in these schematic illustrations, for the possible need for a more sturdy base. One of the benefits of such a design is its visual permeability - you could set this against a wall or simply in the middle of a room as it is essentially see-through.
On the actually-built side of things, these cardboard bookcases put round into practice. The spaces created within them are somewhat challenging from a functional standpoint but visually they are very impressive. It goes back to the age old furniture question: do you design with a function in mind or let users figure out their own functionality?