The first strange thing about this 13th-century tome is its sheer size. The book is three feet high. The second thing about it is that it's handwritten, and it's all the work of one monk. To completely fill the 310 pages with handwriting so small would likely have taken ten years or more.
The third - and the most frightening - thing about it is that it contains a gigantic illustration of the Devil, and twelve pages have been torn out. For these two things, there is no known explanation.