When James Agee died of a heart attack in 1955, he left behind a wife and four children, $450, and the manuscript of the autobiographical novel “A Death in the Family.”

Hoping to help provide for Agee’s widow and children, a friend of Agee’s, David McDowell, decided to edit and publish “A Death in the Family.” It won the Pulitzer Prize for fiction in 1958 and became an instant classic.

But, contrary to McDowell’s claim in a prefatory note that the text appeared “exactly as [Agee] wrote it,” his editing was extensive. Now, for the first time, “A Death in the Family” is being published as Agee wrote it, in the first of a planned 10-volume series of Agee’s complete works coming out from the University of Tennessee Press. The book will be on sale this month; four of the previously unknown chapters are in this month’s issue of Harper’s magazine.

It was an English professor at the University of Tennessee, Michael Lofaro, who solved the mystery of Agee’s original intentions for the novel. In 1988, McDowell’s son wanted to sell some of his father’s papers to the university, and Mr. Lofaro was called in to appraise them. Going through the materials, he discovered what seemed to be Agee’s primary manuscript for “A Death in the Family,” including two previously unknown chapters, and ancillary notes on the novel. Using these, and another version of the manuscript held by the Harry Ransom Humanities Research Center at the University of Texas at Austin, Mr. Lofaro was able to reconstruct the original text.

Publication of the restored version had to wait 20 years, because of a dispute between the University of Tennessee and the James Agee Trust. When the Trust realized that McDowell’s son had sold some of Agee’s papers, it sued the university unsuccessfully to recover them. As a result of the dispute, the then-trustee of the James Agee Trust, Mary Newman, wanted nothing to do with the papers. In 2002, Paul Sprecher, the husband of Agee’s daughter, Deedee Agee, took over management of the trust, and he was interested in Mr. Lofaro’s project. “I felt like, well, a feud’s a feud, but eventually there’s no point,” Mr. Sprecher said in an interview. “It seemed to me that Michael Lofaro had a vision that was potentially re-energizing of the material.”

Both Mr. Lofaro and Mr. Sprecher described the novel as Agee wrote it as darker, at least in the beginning, than the version McDowell published. The original introduction is a nightmare sequence in which the son carries his father’s body around Knoxville; a central image is of the head detaching from the body. McDowell cut this and inserted as a prologue “Knoxville: Summer 1915,” an unrelated essay Agee had published in 1938 that is an elegiac reflection on his childhood.

While Agee’s manuscript proceeded chronologically — from the young protagonist’s early memories of his father to the automobile accident that killed him and its aftermath — McDowell removed the early chapters and then re-inserted sections of them as flashbacks after the father’s death.

Both Mr. Lofaro and Mr. Sprecher said that the novel as McDowell altered it was probably more salable than Agee’s own version. McDowell “had a good eye for publicity and a good eye for sales,” Mr. Lofaro said. McDowell’s first priority seems to have been earning money for Agee’s wife and children, he added.

The published novel, Mr. Sprecher said, “became a sensation. It was sold to the Book of the Month Club. It was a ’50s novel.” Agee’s version, he added, “probably would not have won the Pulitzer Prize.”

Mr. Lofaro felt, however, that the record needed to be set straight. “Taking on a Pulitzer Prize-winning novel is not something you do lightly,” he said, “but [McDowell] said literally that this was Agee’s final manuscript.”

The other nine volumes of the University of Tennessee project, which will come out over the next decade, will include much more previously unpublished material. After Agee’s death, Mr. Lofaro said, his friends tried to publish much of his unpublished work, but they selected primarily those writings that fit their idea of how they wanted him to be remembered.

Robert Fitzgerald, who edited collections of Agee’s poetry and short prose, made conservative choices, Mr. Sprecher said. “A certain image of Agee was created [by his friends] in the late ’50s and ’60s,” he said. “It was the tortured artist with enormous promise who dies too soon, but it was not a heavily political figure.”

The published Agee writings leave significant gaps, Mr. Lofaro said. “You’re not going to find his early engagement with left-wing politics, or his involvement with the avant-garde set in New York.” These gaps will be filled in by the University of Tennessee volumes, as well as by a new biography of Agee currently underway by an editor at the New York Times Book Review, Dwight Garner.

The collected works will also include some dozen never-before-published screenplays, including Agee’s original screenplay for “The Night of the Hunter.”

“Hollywood legend has it that Agee delivered to [the director Charles] Laughton a text the size of the New York City phonebook, which Laughton said was completely unusable,” Mr. Lofaro said. “Laughton said he had to rewrite it himself and just left Agee’s name on the credit out of charity.”

Shortly after he took over the Trust, Mr. Sprecher was looking in some boxes and found a pristine manuscript of Agee’s original screenplay. It was indeed long — 300 pages — but an examination also made clear that Laughton had produced his screenplay essentially by editing down Agee’s.

Mr. Sprecher said he was eager to see what the critical reaction to the new “A Death in the Family” would be. The current deal, with Vintage, for the paperback edition of the edited text runs out next year; at that point, he will decide whether to re-issue that version, or publish this one in a popular edition. The Trust is being represented by the agent Andrew Wylie, who is also representing Raymond Carver’s widow in her effort to get published a new edition of “What We Talk About When We Talk About Love,” with Carver’s stories in their original versions, prior to their drastic editing by Gordon Lish.

Of the probable response to the new version, Mr. Sprecher said, “I’m sure there are those who will say, ‘I love ‘Knoxville: Summer 1915,'” or ‘I love the flashbacks.’ [But] most people in my circle think it’s good and fresh.”