Nietzsche scholars in general adopted the opinion of Kaufmann, who immediately identified the book as a forgery in a 1952 article. Evidence against the book cited both by Kaufmann and later commentators includes chronologically unsound information, such as a reference to an 1898 incident, incongruous references to Marxism and the city of Detroit (globally unknown in the late 19th century), a seemingly poor grasp of philosophy, and the book's sexualized pulpy content.
Nevertheless, some minority views hold the work to be authentic. Beginning in the mid-1980s, a handful of articles began to call for its reevaluation, including references to more recently discovered journals and letters from Nietzsche and Cosima Wagner. Amok Books' 1990 edition reprints many secondary articles on the subject, and includes an original introduction calling for a reevaluation of the book. Nietzsche scholar Walter K. Stewart, in his 185 page monograph Nietzsche: My Sister and I — A Critical Study published in 2007, argues for the original's potential legitimacy by conducting a point-by-point analysis of Kaufmann's book review. In his 2011 followup, Friedrich Nietzsche My Sister and I: Investigation, Analysis, Interpretation, Stewart uses direct textual analysis to argue that whoever wrote My Sister and I was intimate with every aspect of Nietzsche’s life and perspective.