I translate here directly from the German:
Faust’s Book of Compelling Hell (Höllenzwang)
In the church at Zellerfield, there lies secured by an iron chain the Book of Compelling Hell. It was written by Doctor Faust. Few are able to read it, and it is extremely dangerous to read. He who wishes to read it without losing his life must be able to read it forward and then backward. If you read it forward, then the Devil appears. If you read it backward, he vanishes again. If anyone reads the Book of Compelling Hell forward and cannot read it backward again, then the Devil will do the rest.
Source: Hermann Harrys, Volkssagen, Märchen und Legenden Niedersachsens, vol. 2 (Celle: Verlag von E. H. C. Schulze, 1840), 20.