I’ll Never Ever Look At Books The Same Again After Seeing These Hidden Messages. Wow.
Holy cow, this is cool. Make sure to watch the gifs! "It’s very possible that one of your battered old books contains an amazing secret called a “fore-edge painting,” which is an illustration that is hidden on the edge of the pages of the book. The technique allegedly dates back to the 1650s. You can see the painting by bending together the pages of the book, just so you can see a small piece of each page."