Joannes Faustus (portrait).

17th century German portrait of Faustus. Artist Unknown.

Although often displayed as a portrait of Johann Georg Faust, this is likely a portrait of Johann Fust, a printer from roughly the same area who (a generation of so earlier) was a business partner of Gutenberg. He is holding, not a grimoire, but a copy of their printed Vulgate Bible (Biblia Sacra Latina (1462)). Of course Gutenberg is now known for inventing mass production of books, but Fust (or Faustus) as salesman was charged with witchcraft in France for having more virtually identical Bibles in his possession than a man could produce in a lifetime. Once the nature of the invention was explained, he was released.