FOR SEVERAL MONTHS this year More Magazine teetered along, occasionally providing those interested in behind-the-scenes events in the world of American media with some enjoyable tidbits. But, at just about the time when many More devotees were beginning to wonder whether the thin-and-getting-thinner news monthly was worth opening the mailbox for, More burst on the scene this summer with a totally new format. While the old More dwelled solely on news, and the men and women who make it, the introductory note in the July/August issue said the magazine would now cover advertising, book publishing, film, public relations and marketing. For long-time More readers the change was astonishing and intriguing.

The issue was impressive. There was a terrific article about who was doing the best job covering Carter, entitled "The Best Crystal Balls on the Bus." In a survey of bizarre editorial writing, More came across the Philadelphia Daily News's Richard Aregood, who plugs away at strange causes in an extremely eye-catching way. The seeming abundance of Jews in the media was explored. The magazine was littered with loot, almost as if More's editors had collected little gems for the past few years and decided all at once to show us their splendid collection.

Well, now with More's September issue, it seems that its editors have nothing left to show. And many of the summer's gems have turned to glass. Four out of five letters are devoted to correcting stories from the July/August issue. An explanation at the end of the letters section shatters "The Best Crystal Balls on the Bus" piece by telling us that the writer, Milton S. Gwirtzman, is on Jimmy Carter's staff. Then, as if to rub things in a bit, More's editors note that Gwirtzman's "involvement with Carter in no way diminishes his analysis." Sure. And perhaps Gwirtzman didn't have it in mind to butter up a few national reporters for the homestretch.

Once on the inside More makes it plain that it has nothing to offer those who want to learn how to be better writers. Nor does it have any desire to be critical about America's press, advertising or television. What it does want to do, however, is jam the issue so full with big names as to appeal to anyone interested in the latest gossip in all three areas. Those curious about the seamier side of the press will enjoy reading about "Ben and Sally." T.V. viewers will no doubt want to read about Walter and Walters. Advertising moguls can learn what Ted Bates is up to. And those ubiquitous Times watchers should get out their scorecards: there must be more than 25 familiar bylines in this 56-page issue. Everyone is mentioned pointlessly.

Maybe there's some sort of market for this star-studded blather. But for heaven's sake let Woman's Wear Daily mine it. They do a much better job covering the celebs than More can do anyway. What More should devote itself to is something along the lines of its original creation, something in the spirit of A.J. Liebling's writings on the press. Liebling dealt in matters of substance, giving examples from around the country about what can happen when you have a one-paper town, or how publishers force their biases into print, or how we are privy to such poor foreign reporting. When Liebling wrote on the Times' he didn't dwell on inter-office memos. He would critique the paper and show how, for instance, it may slant a labor story against management or get the facts wrong.

Perhaps More will find that penetrating the mystique that shrouds big names is the only way to make the magazine a financial success. But if that be the way to survive, maybe it would be better if More decided to fold.