The feud has cast a pall over what was billed as an intimate and revelatory tell-all. Ms. Stevens drew on her own conversations with Avedon over the decades, and interviewed many of his prominent friends and collaborators, including Calvin Klein, David Remnick, Twyla Tharp, Donatella Versace, Jann Wenner and Isabella Rossellini. Some of Ms. Stevens’s revelations about Avedon’s personal life are so juicy that they leaked to the gossip pages in advance of the book’s release on Nov. 21: (The New York Post’s Page Six reported on the book’s description of Avedon’s secret affair with the director Mike Nichols and his sometimes withering views of his colleagues and the celebrities he photographed.)

In a release issued on Dec. 20, the foundation compiled a list of factual errors from the book, among them, Ms. Stevens’s claim that she was by Avedon’s side when he died (he was attended only by his family when he died in San Antonio, while Ms. Stevens was in New York City at the time, according to the foundation); that Avedon was paid $1 million a year to join Vogue as a fashion photographer (he signed a contract with Condé Nast that awarded him $1 million over 20 years); and that Avedon photographed his terminally ill father “relentlessly,” taking 50 portraits of him during “fraught” sittings (according to foundation, there were just six portrait sessions).

The foundation also claims that Ms. Stevens based parts of the book on an unfinished, semiautobiographical novel that Avedon was working on for years before his death, in which he blended elements of his past with fiction. “Stevens appears to be lifting various stories out of this fictional work, lightly editing and rewriting them, and then presenting them as both her own work and as biographical fact,” James Martin, the executive director of the Richard Avedon Foundation, said in a statement.

Image Credit... Alessandra Montalto/The New York Times

Mr. Martin said he read parts of Avedon’s novel in progress after his death, when he was sorting through his files and packing them up. He said he asked Ms. Stevens what she wanted him to do with the manuscript, and she said she would take care of it, and took the box and put it under her desk. (When asked to provide examples of overlapping passages from the novel and the biography, the foundation declined to do so.)