Brian Kelly, who has been number two at U.S. News & World Report for the past nine years, will run the magazine following the departure of Brian Duffy announced today by publisher Mort Zuckerman.

“Brian is the perfect guy for the job,” Duffy told The Washingtonian.

Zuckerman’s statement from New York said Duffy was “stepping down to complete a book and to pursue other long-format writing projects.”

Unlike many such statements about changes at the top of news organizations, Zuckerman’s statement appears to be accurate. Duffy left of his own accord.

“These jobs are not designed for 20-year careers,” Duffy said. “They take a lot out of you.”

Duffy has come and gone from U.S. News since he began reporting for the weekly magazine in 1986. He left in 1996 to write for the Washington Post and then the Wall Street Journal. He returned to U.S. News and became editor in 2001.

Duffy ran the magazine through many wrenching changes, including rounds of firings, moving reporters from the print side to the web site, trying to keep circulation up when ad revenues were shrinking.

“It’s a good time for me to do something more about getting my life together,” he says.

U.S. News is the perennial third among the weekly newsmagazines, with Time and Newsweek far ahead in circulation and clout. U.S. News has been trimming staff and promoting its college and hospital rankings on the web site, which has become a more important source of revenue.

Zuckerman is often rumored to be thinking of unloading his weekly magazine, which provides him a page in most issues for his opinion column and invitations to be a pundit on television talks shows.

“Mort supports the magazine without qualification,” Duffy said.

On Friday Zuckerman turned over the magazine to Brian Kelly and left for Australia. Kelly has not been named the permanent editor.

Kelly, 52, came to U.S. News from the Washington Post, where he was a deputy national editor. He also worked at the Post’s Style and Outlook sections. A New Jersey native, he cut his teeth writing for the Sun-Times. From 1985 to until it folded in 1992 he edited Regardie’s, a monthly magazine on Washington business and politics.

At U.S. News, Kelly has concentrated on developing partnerships for the magazine’s web site and growing revenues from its college and hospital rankings.

Brian Duffy will be working on two books—a history of spying during the Revolutionary War and a thriller on which he is collaborating with an FBI agent.

He believes U.S. News’s prospects are good.

“U.S. News is a great brand,” he says. “They will figure out the business aspects going forward.”