NEW YORK — In a move that stunned the publishing industry and Conde Nast insiders, James Truman, editor-in-chief of Details magazine, was named editorial director of Conde Nast Publications, Inc. He succeeds Alexander Liberman, 81, who has held the job for 31 years. Liberman will become deputy chairman, editorial.

Truman, 35, is only the second editorial director in Conde Nast’s history. The moves are effective April 1.

Succeeding Truman as editor-in-chief of Details is John Leland, senior editor for Newsweek’s lifestyle section. Under Truman’s editorship, the circulation of Details has more than quadrupled to 480,000 from 100,000.

The abrupt appointment is chairman S.I. Newhouse’s second major move to rock the halls of Conde Nast in two weeks. This month, as reported, Steven T. Florio was named president of the company, succeeding Bernard Leser, who will become chairman of Far Eastern operations.

“I was still digesting the Steve Florio announcement,” said Art Cooper, editor-in-chief of GQ. “The earth is moving here as much as in L.A.”

“My downtown days are over,” Truman told WWD.

In describing his new job, Truman said, “It’s a position where I’m available to be consulted and offer suggestions to all the magazines. I don’t dictate what the magazines have in them. That’s the way it was under Alex, and that’s the way it will be under me. I’ll see all the magazines before they go to press,” he noted.

Conde Nast editors contacted Tuesday said they were surprised but generally pleased with the appointment and downplayed what the reporting structure would be. For some editors, in fact, the reporting structure remains a mystery.

“The title speaks for itself,” said Florio. “I don’t believe James will be heavy-handed about it. I know that Mr. Liberman has advised all the editors from time to time, and I would expect James will maintain that relationship. Some will invite him to work with them; others won’t.

“The mandate the two of us have received is to run the company. Si and Alex have said, ‘Here’s the next team,”‘ Florio said of his and Truman’s appointments.

Historically, Conde Nast editors have reported to Liberman, who had final approval over layouts and stories in all Conde Nast magazines, with the exception of GQ, where Cooper several years ago demanded and got independence from Liberman’s authority.

Liberman was instrumental in the launch of Allure, Self and Vanity Fair and participated daily in Vogue.

Asked about Conde Nast’s reporting structure, Anna Wintour, editor in chief of Vogue, said, “It’s not boarding school here…it’s not cut and dry.

“We talk to Si. We talk to Alex. The reason we love working for Si and Alex is they let us have our independence.”

Wintour explained that Liberman “certainly advises and looks at everything, and he’ll suggest changes and make changes.” She said that Liberman will continue to be involved with Vogue.

“Alex is an art director,” said Wintour, noting that Truman will define the job in his own way. “You can’t say that James will come in and be Alex.”

“I’m very proud of James,” continued Wintour. “He’s a great friend of mine. I brought him to Vogue and suggested him for Details.”

Wintour denied rumors that she turned down the role of editorial director. “I was never offered the job. I would have been lousy at the job and James will be brilliant. He has my total and full support,” she said.

GQ’s Cooper said he did not know whether editors who reported to Liberman would now report to Truman.

“Those of us who don’t deal with Alex will continue on as it was,” said Cooper. He described Liberman’s role of “editorial director” as, “if you need assistance, he’s there for you.”

Russian-born Liberman, 81, has been editorial director of Conde Nast since 1962. Hired by Conde Nast himself, Liberman joined the Vogue art department in 1941, and in 1943, was named art director of Vogue.

By 1960, he was general art director for all of the Conde Nast magazines before assuming his current post. Liberman is also an acclaimed artist, writer, sculptor and photographer.

Truman, who was born and raised in England, became editor in chief of Details in 1990. Prior to that he was features editor at Vogue.

Liberman’s new duties will include periodic travel to work with the company’s European editors.