So I've been looking up things on the Holographic Principle for a while now, but there's still a few questions I have. As I understand it, the Principle says that if I drop a book into a black hole the book's information would be 3D inside the black hole and it would also be 2D on the event horizon. My question is, are there two books one 3D and the other 2D? Or is there just one book that is 2D and the 3D version is a projection that somehow emerges from the surface? In other words, when I drop a book into a black hole, is a copy created when it passes the event horizon or is there just one book in the entire system? If I'm unclear about this let me know. Also, I'm not a physicist so please keep answers layman.