The books inside out

A system I saw in an interior design store in London (but I didn't have my camera): all the books stood backwards, or inside out - with the spines to the wall and the pages to the room.
(Since I didn't have my camera the picture is from here.)
I will not try this system myself, as it will be much too monochrome. Of course books with dyed or gilt fore-edges will stand out, but the rest will just be varying shades in the scale from white to yellowing off-white. (I don't like white.) I wonder what organizing system these people have, though - it'll have to be very strict, if they're going to find anything...