There are 700,000 copies in print of "Who Runs Congress?," a study by the Public Citizen's Congress Watch. The figure quoted in Tuesday's edition of the Style section was incorrect.

"I know the book has a sense of credibility," said Sen. Howard Metzenbaum (D-Ohio), waving the bright red, third edition of "Who Runs Congress?" "I looked in the index and it mentions Russell Long's name 35 times and mentions mine once.So I know it's entirely accurate."

Metzenbaum shot a long look at the author, Mark Green, the head of Public Citizen's Congress Watch, and Ralph Nader, the boss of Congress Watch, and continued speaking over the laughter in the Rayburn Building. "Someone told me consumerism is no longer popular buth those men on my left have proved that it is." He paused for effect: "And I'm glad someone is on my left."

That was the jocular tone of the book party for "Who Runs Congress?" an inside, investigative study by the Nader lobbyist with 70,000 copies in print. The new Bantam paperback is a revised and updated version of its best-selling first edition. Congressmen like Robert Drinan (D-Mass.), Richard Ottinger (D-N.Y.), Henry Reuss (D-Wis.) and James Shannon (D-Mass.) all checked out the index with dramatic fanfare.

"And it's with trembling hands that I am reading this, Ralph," joked Reuss, who was dashing in from an American Association of Equipment Lessors reception across the hall. The Lessors had a hearty buffet and almost all male guests while the Nader party had bowls of peanuts, cheese, apple juice and wine and a mixed crowd. Reuss said, "the two are not wholly incompatible. I told Ralph that the ultimate goal of that group is to create a market for good urban transport systems. That would save energy and fight inflation."

On the 60 books published under the Nader group's auspices. "Congress" is the runaway favorite. Green, who also wrote the books on Washington lawyers and major corporations, found the updating a sign of the changing times. "The first edition has long profiles on Mills, Hays, and Nixon. Now they are like from another era and we eliminated the whole chapter on impeachment and Watergate," said Green, as a scene-stealer, his 8-month-old daughter Jenya, crawled around him. "We had to expand the chapter on Lawmakers as Lawbreakers because many more had been indicted and run into ethical problems."

Though the dominant spirit congratulations continued, some work of Congress Watch continues also. James Shannon, at 27 the youngest member of Congress, had been approached by Nader's Raiders Carolyn Brickey and Sidney Wolfe for help to work against the bill that proposes to exempt the professional standards review organizations from the Freedom of Information Act. The three were caucusing on their progress at the party.

"I wasn't aware of the issue until they came to see me. But I was sympathetic to the need for the public to know the ratings of doctors and hospitals," said Shannon, who is the son of a physician. "They are good lobbyists because they manage to avoid self-righteousness." Wolfe commented that the other Nader groups find the "Congress" study of a good reference. "With the information you can begin to judge who is more likely to give in to American Medical Association pressure," he said.

The popularity of the book, said Nader, is based on its readability. And, he added, "It's far more appealing outside Washington. People will say they had no idea Congress was as corrupt . . . and the reason is they see specifics.This is not a blanket indictment." And Reuss nearby said, "If I have been [mentioned favorably] it's a profound book. If not, then it's a lot of miserable dribble."