It’s a mysterious book that in its day was believed to contain all human knowledge. But why did medieval people believe that the author sold his soul to the devil to be able to write it? The "Devil’s Bible," a behemoth volume weighing in at 165 pounds, believed to have been produced by a single monk over the course of decades in the 13th Century, is the focus of a documentary that was featured on the National Geographic Channel.The "Devil’s Bible," a behemoth volume weighing in at 165 pounds, believed to have been produced by a single monk over the course of decades in the 13th Century, is the focus of a documentary that was featured on the National Geographic Channel. Less