On a recent afternoon, Ms. Thornton, who oversees collections and exhibits, showed off the results of that winnowing, displaying a detailed catalog and a sampling of documents on a long table outside the library’s Rose Main Reading Room. The Brodeur collection appeared carefully labeled by subject and date. There were folders containing fan mail from readers (one called an article he had written for The New Yorker “extremely provocative and well-researched”). There were copies of letters from Mr. Brodeur to his colleagues at the magazine (including an angry missive to Seymour Hersh, who had backtracked on an endorsement of a much-debated Brodeur book about the dangers of electrical power lines in 1997. Mr. Brodeur called him “craven” and “lame.”). And there was an unfinished draft of a novel, titled “Coral Sea,” about an investigative journalist who stumbles on an important secret.

Ms. Thornton said that before last year, Mr. Brodeur’s papers had been largely undigested. The documents, she said, “had no catalog record, no archival finding aid, no collection guide.” She added: “The collection was not usable.”

But those claims have pitted the library’s current staff against a highly regarded former colleague, Mimi Bowling, a senior curator who contended in letters to Mr. Brodeur that the library had finished organizing his collection by 1997, around the time she invited him to tour the archives. Any claim to the contrary, Ms. Bowling wrote to Mr. Brodeur, “is simply not true.”

Ms. Bowling, who now consults as an archivist, declined to comment, but did not dispute the authenticity of her letters.

Archivists said that 18 years was an extraordinarily long time for a library to process an individual’s papers, and they wondered if the library had changed its mind about the value of Mr. Brodeur’s donation. But they noted that Mr. Brodeur had explicitly given up all rights to the papers when he signed a “deed of gift” donating them to the library.

According to that deed, the library “reserves the right to return” any items it wishes and “may dispose of the same as the library determines in its sole discretion.”

Even so, Richard J. Cox Jr., a professor of archival studies at the University of Pittsburgh, said the library might have mismanaged the situation. “Waiting 18 years, coming out of the blue — that sounds like not necessarily the best way to handle this,” he said.