Margaret Truman, the longest running and most commercially successful of the presidential offspring fronting mysteries, offers no hint in any of her books, beginning with "Murder in the White House" (1980), that she has a ghostwriter, a collaborator, or even a literary mentor. Her "Capital Crimes" novels, which usually use as background Washington, D. C., landmarks (the Kennedy Center, the National Cathedral, the Pentagon, the National Gallery, the Library of Congress, etc.), provide plenty of historical tidbits and tourist information. They are far from distinguished detective fiction, but they do rank as above-average celebrity mysteries.