Use your books to make a shelf!
I saw this new product at chiasso. Very cool. Their desciption:
Amazing disappearing shelf turns ordinary books into an ingenious, modern illusion. Simply set a large hardcover into the shelf then add a stack of books. The bottom book should be the largest in the stack. Two small, hidden rivets hold the hardcover book in place, so the bottom book becomes the shelf. Hang a few of these modern metal bookshelves to create a cool, floating library. Powdercoated steel. Installs easily with two screws. Holds up to 15 lbs.