Would you stick your books on the back of a door?
I know that sounds like a mad question, but look!
Spotted in Marie Claire Maison by those amazing Apartment Therapy people, the books are held up by the "Sticklebook". The innovative design comprises an aluminium extrusion which acts as a bracket and polypropylene combed strip that grips the cover and pages of paperback books. The shelf is screwed onto the wall which itself helps support the weight of the book and is an integral part of the design. It is totally secure and fall-proof."
Hmmm, I have crappy doors in my house that I wouldn't really care about putting holes in. But how is the shelf screwed into the wall. Well, anyway, having more books innovatively displayed around my house would make me very happy. :^)