Parry, a former A.P. and Newsweek reporter, offers a name- naming book on the herd mentality among Washington's opinion-makers and accuses the Reagan Administration of mounting a domestic disinformation campaign. The idea that Washington is ruled by conventional wisdom is itself fairly conventional wisdom. The overt point of Parry's study, then, is unsurprising--that nobody in our nation's capital can take a step not dictated by what he or she is supposed to think. But Parry also states that successive Republican administrations made an active, secret, and highly successful effort--using CIA-trained personnel and psychological warfare techniques--to suppress adversarial media outlets and to get Middle America to accept military intervention as a legitimate policy option. The Reagan and Bush Administrations' ``public diplomacy'' triumphs can be seen, says Parry, in the vilification of the Sandinistas in Nicaragua, the railroading of former US asset Manuel Noriega, and the willingness of Americans to go to war for a corrupt monarchy in Kuwait. Parry points the finger at Washington pundits, notably at The New Republic and The McLaughlin Group, who, he says, disseminated the White House line unquestioningly. The author--who appears to have a hard newsman's dislike of opinion journalism (``Rather than punditry, the public must insist on the facts, pure and simple'')--is credited with breaking the Iran- contra story for A.P., but his efforts to report the story fully, he says, were thwarted by Administration officials as well as by his superiors, and he seems at times almost bewildered with disillusionment. Earnest and troubling--though Parry's analysis of the problem is not a strong enough framework for his lengthy, digressive recaps of such recent history as Iran-contra and the Gulf War. The force and momentum of his major point, moreover, are often mired in the book's signal virtue: a mass of newspaper-style detail.