The editor-in-chief of U.S. News & World Report for the past seven years, Brian Duffy, said he had resigned from the Mort Zuckerman-owned newsweekly yesterday and plans to write a book on the American Revolution.

Duffy, who will be replaced by Executive Editor Brian Kelly, presided over a radical overhaul of the magazine in which it retreated from hard news to concentrate on its top-selling guides.