The Nietzsche scholar, Professor, Dr. Karl Schlechta, left at his death his private "Nietzsche library", which he called " ein kleines Archiv " (small archives), to his daughter Eva, Friederieke, Margarethe Nordentoft, born Schlechta. The collection was in her custody from 19 February 1985 till now, June 2002, when it has been passed over to The Faculty of Theology, University of Aarhus. It is accessible by prior arrangement with the Faculty Librarian.

The collection comprises the heavily censored Nietzsche edition of 1933, complete with the entries requested by the Third Reich and the later reentries of the original wording, which had been crossed out in black. It comprises Karl Schlechta's critical Nietzsche edition in three volumes of 1956 (Munich, Hanser Verlag) and later study editions. It also comprises Karl Schlechta's book " Der Fall Nietzsche " (The Case "Nietzsche") of 1959, including the discussions caused by this book, which deals with the disclosure of the forgery and the editing of Nietzsche's works and letters, undertaken by Nietzsche's sister, Frau Elisabeth Förster-Nietzsche. She wanted the aphorisms to the theme " Der Wille zur Macht " (Will to Power) to be edited as a major work, but it did not exist in that form from Nietzsche's pen. The works done by Karl Schlechta during his stay as a director of the Nietzsche-Archiv in Weimar from 1933-1938 provide a glimpse of these initiatives and research achievements.

The collection comprises essential works concerning the Nietzsche research as well as contemporary works of psychology, anthropology and social science.

Materials in the collection also include " Der musikalische Nachlass, Basel 1976 " (The Musical Remains, Basel 1976) - Nietzsche's compositions, which show his status in the contemporary romantic German Lieder and composition tradition.

Nietzsche's original handwritings from the Nietzsche-Archiv in Weimar were for some time after World War II removed by the Soviet occupying power (Weimar belonged to the Soviet zone) but they were later returned. Karl Schlechta has also returned to Weimar the handwritings which were in his possession at that time.

The collection gives the picture of a world in fundamental change as well as the impression and analysis of a coming catastrophe. The collection also shows how Nietzsche and his influence was understood and interpreted by those who already knew and those who "were lucky to have been born late" and thus were able to look without the ballast of history. In " Der Fall Nietzsche " Karl Schlechta repeatedly emphasizes that Nietzsche was not a prophet but a sharp and mercyless analyst, "who then as well as now is not being read, but quoted".