A children's book.
So there was this book I had when I was a kid. everything was illustrated in black and white. When you finished the book, you turned it upside down and read it 'backwards,' and all the pictures from the first time through now represented something else in reverse color. It's really freakin' cool, and I was just reminded of it earlier tonight but I can't remember it. And I highly doubt I could easily search for my above description anywhere online.
Anyone know what I'm talking about? Please?