The mysterious treatise, which stands at the end of medieval German mysticism and is mostly referred to as 'The Franckforter', was first published and introduced by Luther in 1516. It then went through over seventy editions and remains a milestone in spiritual literature. It is the most important link between medieval spirituality and both Reformation and Baroque spirituality. Alois M. Haas presents previously unrecognized insights into the actual content of the treatise based on his own research. In the third edition, he expands with a concluding consideration, highlighting some points of connection that Luther discovered in the 'Franckforter' for his Reformation.