This seems like a design student project, but in fact it's in production:
Designed and manufactured in Iceland by design-build firm Agustav, the simply-named Book Rack is aimed at readers like my wife, who prefers to borrow books from the library rather than own, or like my friend Elaine, who gives away every book shortly after reading it to keep inventory low. (She picked up the habit because her job required her to move frequently.) It's also a handy object for those who read multiple books at once and want to keep them at hand.
The waxed cotton string serves as both the bookmark and the suspension element for the "shelf," the tiny wooden plate on the bottom. "The books rest on a small wooden plate so the pages stay intact," Agustav writes. "The plates can be moved back and forth on the bottom of the book to control the height of which the book hangs, making it possible to line different sized books up in a straight line."
It wouldn't work for me because I'm a book hoarder, but I greatly admire the different thinking here and the execution.