David Halberstam, for one, wasn't the least surprised to find that among "the powers that be" (from his book of the same name) one power was missing last night.

"I wouldn't accuse them of grace under pressure," Halberstam said rather archly of the Columbia Broad-Casting System, about which he has written less than flattering things in the book, just published by Alfred A. Knopf.

When excerpts of Halberstam's book came out in Harper's, according to the author, William S. Paley was so angry that CBS "seriously considered buying Harper's so this would never happen again."

Paley, who some people say is CBS, reportedly was enraged over Halberstam's comments on the network's priorities: ratings over quality. ("My God," said Halberstam last night, citing one example, "he killed his favorite show - my favorite, too - 'The Paper Chase.')" Diane Rennert, who arranged the party at the Sheraton-Carlton Hotel on behalf of the Association of American Publishers, said she had invited CBS's man in Washington, William Small, "but I never heard back from him, and he always comes to my other parties. I hadn't thought about it but maybe it is an insult."

Regardless of whether it was intended as an insult, the absence of a CBS representative is the kind of juicy stuff that adds to an author's panache, and may even help sell a few books. Another slight, this one definitely intended, according to Halberstam, was when CBS turned down an invitation for Paley to appear on the NBC "Today" show after hearing Halberstam would be on it. "They said that Mr. Paley would appear the next day."

There was no such boycott, apparently, among the other three "powers" - The Los Angeles Times, the Washington Post and Time - all of which sent representatives last night. They included Jack Nelson of The Times, Don Graham and Ben Bradlee of The Post and Murray Gart, now of the Time-owned Washington Star and previously with Time, and correspondents from both of the other major networks were there as well.

"Halberstam's a master story teller but from everything I know about The Times, what he says is right on the money," said Nelson, whom Halberstam describes in the book as "one of the two or three best-known and most respected investigative reporters in Washington, a man of almost unique abilities."

There were other "powers," past and present, and not all of them are associated with media. When W. Averell Harriman arrived with Paul Warnke, Halberstam whipped out a pen to inscribe on the fly-leaf of his book: "To Averell Harriman, a power that is."

In a spech he had written out in longhand on yellow foolscap ahead of time - "I don't usually do that but the publishers association asked me so I felt I was speaking for more than just myself," he said - Halberstam grew rather loftly.

"I wrote this book to try to explain a social phenomenon - the rise of a national media prism through which events are perceived. I wanted to move away from the ideological definition of the press and try to understand its strengths and weaknesses as they are, away from the prejudice and conspiracy theory. As we are better understood, we serve better; and as we better understand our own role and our own flaws - that many of our own flaws are self-imposed - we become better and perhaps more honest."

Not that Halberstam was entirely without humor. "The Powers That Be" ranks No. 2 on some best-seller lists, he told the crowd of more than 100 journalists, administration officials and members of Congress. "Only the Scarsdale diet is ahead." Which reminded him of his other book, "The Best and The Brightest" and how he was still at Harper's when it came out "behind the Atkins diet. One day I got a call from somebody who said he was Robert Atkins, suggesting we collaborate on 'The Best and the Fattest' - I knew then it was Willie Morris."

Later, Halberstam's sister-in-law Elliott Jones, wife of Dr. Michael Halberstam, said she wished he had told more "funny things" such as the Atkins story.

"There is a familial tendency to take ourselves too seriously," said Michael Halberstam, who is also an author of considerable success, to such an extent that stories about sibling rivalry persist. "Bug off," Michael told one guest who jokingly brought up that possibility.

"Really," Michael continued, "David is the best reporter of our generation. In the 1920s and 30s you had John Gunther and William L. Shirer. In the 1960s and '70s it's David."

Across the room in the receiving line, where he was behaving as a guest of honor should, David Halberstam added his own disclaimers to questions about sibling rivalry: "Nah, nah, Michael has his life, I have mine. He has a good life. We see each other a lot, more than most contemporary brothers."

As for Michael's books, "Well, his first one was on pills and that wasn't so successful," David said, going on to name two other books by Michael, the latest being "The Wanting of Levine," which has been successful. CAPTION: Picture, W. Averell Harriman with David Halberstam, by Tom Allen - The Washington Post