I have a book case which has some metal trellis at the sides and the books are difficult to get out [probably not meant to be a book case] so last year I made some faux books out of polystyrene. I covered the front and parts that could be seen with paper. I found some images of books, altered the shape where needed and printed them on the ink jet. Even though they were coloured I painted over them with a thin coat of acrylic. From a distance they look like books, but if you removed them you would find that they are strange shapes! They also help to keep the other books from falling over.