A pile of books floating in air is not much of a difficult task to show in a picture. Normally any person would think it to be either a cool trick or the result of some Photoshop tweaking. It is actually a shelf attached to the wall on which the books have been piled up. The shelf is a steel structure that is mounted on the wall. When books are arranged, it imparts an illusion as if the books are  magically suspended in air.

The picture below shows how to set the shelf  into the lower most book. When done other books are kept on top for the floating effect. It is called the Invisible Book Shelf or Floating Book Shelf and is priced around $20.00. See here if you are interested.