A forthcoming Susan Sontag biography claims that the renowned writer penned her husband Philip Rieff’s seminal book, Freud: the Mind of the Moralist.

The biography, Sontag: Her Life, by Benjamin Moser, refers to “textual and anecdotal” evidence that Sontag, then in her 20s, was more than just a co-author of the book, something which has been long-established.

Sontag met Philip Rieff at the University of Chicago when she was just 17 and married him 10 days later after attending one of his lectures. The pair shared an intense 10-year marriage before separating in 1960; Sontag moved to New York while Rieff continued his academic work in Chicago.

Sontag was always acknowledged in the preface of Freud: the Mind of the Moralist but editions published after 1961 no longer cited her as a co-author. It’s claimed in Susan Sontag: An Annotated Bibliography that the removal of her contributions after this date were a condition written into her divorce settlement with Rieff.

For his new biography, Moser spoke with close associates of Sontag who had previously not opened up about their relationship with the writer, and was given access by the Sontag estate to materials withheld from the general public. He concludes in his biography that while Freud: the Mind of the Moralist was based to some degree on Rieff’s research: “He almost certainly did not actually write the book upon which his career was based.”

Moser quotes a letter sent by Sontag to her mother saying: “in third gear now on the book – working about 10 hours a day on it at least” as well as citing correspondence with her friend Jacob Taubes who in a 1958 letter told Sontag: “You cannot give your intellectual contribution to another person... It could be the ruin of Philip if he dared to come out shamelessly without your signature.”

You can read here how Sontag’s seminal essay Notes on Camp informed our ranking of this year’s Met Gala looks. Moser’s book is due to be released on September 17.