Jonathan Karp, the publisher of Simon & Schuster, said in an interview on Saturday that the book was “a major journalistic feat.”

“He did rely on some anonymous sources, and I’ve talked to him about that,” said Mr. Karp. “I believe that his sourcing is strong on the basis of all of the on-the-record sourcing that is unimpeachable.”

Mr. Karp said of the “big reveal” of the unpublished manuscripts, “if and when this happens, I would expect it to be one of the biggest publishing events of the year, if not the decade.”

Together, the film and book provide a highly detailed, if somewhat unconventional, tour through the life of an author who landed with the Allied invasion of Normandy in World War II, was among the first to enter the Kaufering IV death camp during his service with counterintelligence troops, suffered mental collapse, then returned to the United States — with a German wife, Sylvia Welter — where he found literary fame.

Among their more tantalizing revelations, Mr. Salerno and Mr. Shields provide little-known details and photographs of Mr. Salinger’s first wife, Ms. Welter, a German citizen who married him after World War II. At the time, in 1945, Mr. Salinger was working as a counterintelligence agent investigating Nazis who were in hiding.

But the book notes suspicious elements of Ms. Welter’s life that suggest she may have been an informant for the Gestapo, a possibility that surfaced among Mr. Salinger’s friends in the post-War era. The marriage would not last. Weeks after the newlyweds returned to the Salinger home in New York, “she found an airline ticket to Germany on her breakfast plate.”

Another relationship described in the book and film will provide plenty of intrigue to Salingerologists: after the war, Mr. Salinger met a 14-year-old girl, Jean Miller, at a beach resort in Florida. For years, they exchanged letters, spent time together in New York and eventually had a brief physical relationship. (She said, in an interview in the film and book, that Mr. Salinger dumped her the day after their first sexual encounter.) Ms. Miller said in the book that Mr. Salinger once saw her stifle a yawn while talking to an older woman and borrowed the gesture for one of his short stories, “For Esmé — With Love and Squalor.”