TO MIX METAPHORS, television people get all the ink. Dan Rather's new book about journalism has been selected for the Book-of-the-Month Club; Lou Cannon's new book about journalism probably will not be. That is less a test of relative merit than a sign of the times.

Rather's new book is fascinating - the kind of story you try to finish in a day or two and you don't forget: Cannon's Reporting is a contribution - a contribution to our understanding of what news and journalism are, what they aren't, what they might be and what they can probably never become in our society.

Reporting is actually a series of 14 candid, nicely written and clearly titled essays. Each essay is about a single topic - the kinds of people who become journalists ("Reporters"), the blases reporters are likely to bring with them ("Values"), or the kinds of biases they are likely to learn through the trade ("The Biases of the News Business"). There are also chapters entitled "Frustrations" and "Limitations." But in a way most of the book is about the frustrations and limitations - including Cannon's own - that journalists face trying to cover local or national politics.

What struck me first and most about the book is that it is not simply Lou Cannon's personal reflections about his career in journalism. This is as serious a piece of real scholarship as the formal documentation implies. Try to remember another book of its kind by a journalist with more than 120 sources entered in the bibliography as well as 125 footnotes included in the text.

Cannon has had the opportunity to know - and to interview specifically for this book - most of the current luminaries in the national press corps. Much to his credit, however, he avoids writing a collection of stories about famous journalists he has known, or a travel log about places he has been as a reporter. He uses his interviews effectively but keeps the book in an analytical - as opposed to a descriptive - mode, suppressing personalities, including his own. Of course, Cannon could not ignore his two decades in the news business. But I rather appreciated his ability to weave his own experiences and mistakes into the text without making himself the center of attention.

My favorite "anecdote" in Reporting involves the disastrous setback that Edmund Muskie received in the New Hampshire primary in 1972. As Cannon tells it, he realized in February of that year that Muskie's position as a "front runner" was an illusion. Cannon says that he watched Muskie in New Hampshire as he lost his composure three times in less than a week - each time without real provocation. But because Cannon wasn't sure that Muskie was throwing the New Hampshire primary away, and because nobody else "on the bus" would admit to seeing it, Cannon kept his best opinions to himself and filed some pieces that the pack could appreciate.

Journalists covering a political campaign are rarely able to write that "the emperor has no clothes" - no matter who the emperor may be or how naked. Too often, they are simply uncertain of all the facts, and will not risk damaging a candidate's reputation by writing a story which follows their instincts but lacks sufficient documentation.

Cannon is frank about his profession. The press corps has more than a few "frustrated reformers," he admits, but the journalists tend to be egotistical, petty and voyeuristic. And the newspaper business itself, according to Cannon, has built-in biases for sensationalism, superficiality, the stylized, and most important, false objectivity - being factual instead of being truthful.

The penchant for negativity in journalism - which Cannon recognizes - has slipped slightly into his own book. He just doesn't have much good to say about American journalism. Indeed, his chapter on the "Watergate Legacy" implies that the Watergate years may have been in many ways detrimental to journalism.

In his forward, Cannon makes it clear that he wants to discuss "the news business and its values and motivations" and to go "beyond soap box editorials on freedom of the press." He has. So, we have a good book about journalism, not a polemic.

People who are not "into" journalism may find Reporting too much like a textbook. People who care about the press as an institution will enjoy and profit from reading the book. People interested in the "star system" in journalism will be less impressed.

But in the long run, Reporting will have a significant influence on professional journalism and journalism students. I think that's the way Cannon would like it to be.In this instance, that's the way it should be.