The devil’s Bible is a name given to a 13th century manuscript also known as Codex Gigas (or Giant Book). The name “Devil’s Bible” came about because of a large illustration of the devil it contains (shown below).
(Of course, there is nothing in the Bible that supports this image of the devil, or even the existence of a supernatural devil.)
The book is the largest medieval manuscript in the world and contains many documents other than the Bible, all written in Latin.
There are also legends associated with the book. See this Wikipedia page for more information.