Cgm 99 is a collection manuscript consisting of 176 leaves with mystic texts from the end of the 14th century. Leaf 2r-35v contains two texts by the Flemish theologian and writer Jan von Ruusbroec (1293-1381). On leaf 36r-173r are the revelations by Adelheid Langmann (1306-1375). Adelheid, who came from a Nuremberg dynasty able to take council and be elected to the Council, was a Dominican nun at the Engelthal convent near Nuremberg. She wrote down her revelations at the behest of a lector working briefly in Engelthal. The text material was partly revised, commented and summarised with other reports by an editor.
The focus is on the portrayal of a gifted sister's life, which is being elevated more and more towards being at one with Christ. In the course of her election, the sister becomes the intercessor of the people before God and helps the people find a new strength of faith. The prayer and the concluding correspondence with the prior, the Cistercian Abbot of Kaisheim, round off the work. The life of grace is shaped by the Engelthal literary tradition: in the topos of the so-called "fruits of grace", according to which poor souls are redeemed, sinners are converted and the righteous are strengthened in their actions.
The revelations have been preserved in Berlin, Munich and Vienna manuscripts. The Munich manuscript reports in the third person, the autobiographical material is characterised by the smoothing and substituting of the quixotic final parts. The vision literature by German mystics in the 14th century was reflected in numerous sister's books.