Inventions that no-one invented

There are many things that They have failed to give us. We were so totally promised a flying car by the year 2000, not to mention shiny silver clothes and instantaneous transportation. (I feel particularly aggrieved by their failure to deliver the last one of these. I mean, you can instantly send pictures, videos, audio files and information across the globe, yet when you want to move yourself, you're still sitting there at traffic lights or waiting for a ferry. It's so old-fashioned.) However, I can accept that flying cars might take a little bit of work to produce, but why, oh why, haven't They invented something that will stop books from falling over on shelves?

How hard can it be? I mean, just put a strip of something magnetic on the shelf, gild the bottom edge of the book's pages with metallic paint, and, bingo, all your books stay upright, good as gold. Plus, you also have an instant practical joke you can play on someone, if you insert a magnet in their book with the magnet arranged in the "like poles repel" position, so all their books refuse point blank to sit on the shelf, but leap up into the air and hover there like... well, like flying cars.

And if I can come up with this scientifically-flawless plan over lunch, I don't see why on earth They haven't come up something before now. Won't somebody think of the librarians?