HAVE YOU EVER wondered why William S. Paley and Howard K. Smith weren't speaking at Edward R. Murrows funeral? Gary Paul Gates can tell you; and if he can, rest assured, he will - in Air Time , "the inside story" of CBS News.

The jacket says Air Time is "filled with a seemingly endless flow of inside detail," and I would go along with that. It is also filled with opinions, the preponderance of which appear to be the author's. For Gates, as a CBS News writer from 1970 until 1973, has worked closely with many of the people about whom he writes. "Indeed," as he informs us in a afterword, "there are several passages in this book in which I appear as an invisible participant - an off-camera voice, as it were - although I was determined, from the outset, to avoid the indulgence of the first-person singular. Even now, as I venture forth from the woodwork, I do so with some reluctance."

That reluctance, it seems to me, might have been put to better use earlier - perhaps when Gates agreed to write this book. As a close friend of Dan Rather's (and a collaborator on Rather's Nixon Administration book, The Palace Guard ), Gates may have been a little too intimate with his material to treat it in the detached, objective style he has tried to strike. On the other hand, a gift for trying endless detail into coherent narrative would have aided the effort considerably.

CBS News, as depicted by Gates, is a mean place full of small people. One of the smallest, for instance, was Howard K. Smith before he moved on to ABC. "If his superiors had a high opinion of Smith," writes Gates, "it was nothing compared to Smith's opinion of himself . . . At one point, in early 1961, when a high-level CBS News executive urged him to tone down his more assertive commentaries, Smith said he couldn't do that because the country had just gone through eight years of weak leadership under Eisenhower, and now the President was Kennedy, whom Smith regarded as shallow and as inept as Ike. The country, he proclaimed, was desperately in need of leadership, the clear implication being that he, Howard K. Smith, was the one to provide that leadership . . ."

Although I'm not sure just what it is, I have the feeling that a more charitable interpretation could be put on Smith's remarks, even as described. Charity, however, is not one of Gates' strong suits.

Or take the equally unpleasant sounding case of Fred W. Friendly, president of CBS News in the mid-1960s, who resigned over the network's refusal to carry George Kennan's Vietnam testimony before the Senate Foreign Relations Committee. "Those who were close to Friendly at the time," Gates reveals, "believe he became so enthralled by the prospect of going down in flames over a point of principle that he would have been truly disappointed if Paley and Stanton had relented and given him his way."

"Those who were close to Friendly"? All of them? His wife? His children? I haven't a shred of evidence to suggest that Friendly's motivations were substantially loftier than Gates makes them out, but this unanimity of opinion on the subject among his immediate circle strains credulity.

If I have given the impression that 90 percent of Gates' book is concerned with personalities, petty feuds and dime-store psychoanalysis, then I apologize. It is more like 95 percent. Air Time consists essentially of a string of brief biographies of the significant personages - known and unknown, on-camera and off - who have done time at CBS News since the dawn of television. There is virtually nothing said about the technological or financial end of the news-gathering business, no sense imparted of what it takes to put together an edition of the "CBS Evening News" or a piece on "60 Minutes."

Gates does carry his readers back to somwonderful forgotten moments in TV news history. Walter Cronkite's "You Are There" broadcast on the fall of Troy, for instance. "We are standing outside the tent of Archilles," declares Cronkite. "The place: the plains of Ilium outside the great walled city of Troy. The date: 1184 B.C. And - you are there!" Or Cronkite, again, shouting "Go, baby, go!" as Apollo II leaves Florida for the moon.

And there are engaging anecdotes, like the time that CBS Evening News producer Don Hewitt, fed up with anchorman Douglas Edwards' tendency to look down on his script in preprompter days, truimphantly announced the solution: Edwards would have to learn Braille. (He refused.)

But there is a striking difference between Air Times an, say, The Kingdom and The Power, Gay Talese's equally "inside" history of The New York Times. Talese took a group of largely obsecure newspaper people and, in massive research and graceful writing, brought them to life. Gates has taken a group heavily composed of familiar faces and voices - people we thought we knew - and rendered them two-dimensional, like butterfilies chloroformed and pinned to a board.