NETWORK news, particularly as it relates to NBC, is splendidly related and analyzed in "Out of Thin Air," by Reuven Frank, who was twice president of NBC News.From Huntley-Brinkley (Mr. Frank came up with the famous "Good Night, David,Good Night, Chet," and "Good Night for NBC News" sign-off for their news shows) to the problems with anchors and other famous news "star" personalities, Frank offers a vivid picture from inside the TV newsroom, with all its tensions, frictions, and clashing views of the news. Frank provides a lively and probing look at his years at NBC, reminding readers that it was the 1956 political conventions that really established network news. Reflecting on the current state of network news, Frank deplores the prevailing trend to favor pictures over words, and blames costs for the depleted status of network coverage. "What ultimately robbed television news of stature and cachet was how cheap it is," he writes. "Factual presentation ... cost half as much as entertainment programs. If subject matter could be liberated from our dusty rules, prime time entertainment might ensue. It did. Shows were made to look and sound and feel like news - without the rules."Network television, which started in 1949, had 30 years of thunderous success and prosperity which lasted until the early '80s. Then in 1985, almost simultaneously, ABC, CBS, and NBC were taken over by huge conglomerates. Since then, the network story has been one of fading glory, pressing economic problems, rising competition from cable services and VCRs, and a steady decline in viewers. "Since 1985 ... the networks have been staggered by an earthquake that struck as if in slow motion, cracking their foundations," writes Ken Auletta in his history of network television Three Blind Mice, How the TV Networks Lost Their Way." The book is a fascinating, disturbing, and admirably detailed volume which traces the gradual failure of the networks not only in terms of performance but, quite as effectively, through the personalities that have run network broadcasting, their infighting, their attitudes and philosophies, their inability to see the medium as anything other than a business with barely any responsibilities beyond profit horizons. Mr. Auletta clearly has a close relationship with many of the top network executives. In fact, he says he did some 1,500 interviews with 350 men and women for this book, and he backs up his observations and conclusions with a plethora of facts and statistics to document the networks' downward curve. "Three Blind Mice" is replete with incidents, quotes, and personal confrontations that attempt to explain how the networks fell into their present rut, with their share of the audience dropping to 62 percent during the past season (from a former 90 percent). Worst hit have been the network news departments whose budgets have been drastically cut. They are gradually losing the trust of audiences, Auletta writes, adding: "The new owners speeded the trend to hold news to the same ratings standard as entertainment shows. Each lowered the wall between network news and such tabloid-TV fare as 'A Current Affair. The key networks, which also suffer from competition by the Fox Broadcasting newcomer, are now in the hands of giant corporations which for the most part are new to television. NBC is owned by General Electric. CBS is owned by Larry Tisch of the Loew's Corporation, and ABC's parent is Capital Cities, which does have broadcasting roots. AULETTA'S network history of the '50s, '60s, and '70s is riveting, in part because of the close-ups he provides of the early TV giants who had vision and imagination. It is in the final chapters, covering 1988 to the present, that Auletta draws his conclusions about the future, and they are for the most part dismal. "The new owners began by focusing on costs and ended up thinking more about revenues," he writes. "No one any longer had to sell them on the magnetic power of hit shows." He explains why the new network owners, while taking Draconian measures to cut budgets, simultaneously spent excessively on sports events, approved huge salaries for TV news anchors, and splurged millions on retaining popular series. There will be more audience erosion, Auletta says. There will be more cost cutting. Networks may shift game shows to prime time. Cable will capture more major sports events (what happens to "free" TV?) and "It is no longer unthinkable that one of the Big Three might abandon the network business altogether." Unless the networks consolidate news functions, their news influence "is likely to ebb," Auletta maintains, noting that the three networks - thanks in part to the Gulf war - spent some $1 billion on news during '91. Auletta, a former TV columnist for the New York Daily News, makes good use of his pipeline to the networks' top managements. He pretty much "tells it like it is," which means one is left without a silver lining and with a tinge of sadness that this powerfully influential and once so promising medium has been allowed to descend to such a level of commercial mediocrity.