IT IS THE JOURNALISTS today, not the historians or the novelists, who increasingly define the times. They are the book writers, the hot properties whose works can often command the huge advances, the book club sales, the paperback bonanzas, and, sometimes, the films. Woodward and Bernstein on Watergate, David Halberstam on Vietnam, Gay Talese - and everyone else - on sex, are among those of true talent who have successfully worked both sides of the street: journalism and book writing.

Of Richard Reeves and Kandy Stroud, the latest journalist-authors to enter the lists, it can be said that their talents and their works are not in the slightest complementary. Reeves is a craftsman, stylish and sardonic, and his rendering of the various antics and other sordid activities at last summer's Democratic convention is a small gem. Stroud is a laborious performer, with a leaden style, and a book that surely ought to win some sort of prize for the worst title of the year. My first reaction on picking up her How Jimmy Won was, I'll confess, peevish: any damn fool knows he got more votes. And it's not how he won - the "how" by now being at least a tale told a thousand times - but why he triumphed, and what he'll do with his prize, that are the questions worth pondering. That's not to say her book doesn't provide illumination, and moments of insight. It is just that you have to struggle through it.

In fact, it doesn't require a close reading of the Reeves book to find all you need to know about how Jimmy Carter captured first his party and then the presidency. He was tougher, shrewder, more calculating and he was served by a tougher, shrewder, more calculating crew. But unlike Stroud's, that is not the burden of Reeves's work. What he does, and superbly, is to delineate that cast of political operators who descended, from all competing camps, on New York. He shows us the posturing, the pomposity, the arrogance, the overwhelming sense of exaggerated self-importance of scores of political hustlers - all on the make, all trying to con their way into favor with the great man, the candidate, and thereby win a chance to be lackeys to the throne. A lot of characters, as he makes clear, lust after lackeydom.

What I like about Reeves's book is the way he captures, with a high rate of success, the look and feel and smell of politics and all of its gaudy trappings. In a series of deadly little vignettes, he demolishes a string of people. There is Dick Celeste, the lieutenant governor from Ohio, an inveterate self-promoter if ever there was one, who has his eyes on the presidency himself. There is Phyllis Cerf Wagner, Bennett Cerf's widow and now the wife of New York's former mayor, throwing her weight around by pushing and browbeating young volunteer attendants guarding the VIP boxes. There is the list of three "horribles" compiled by the Democrats' credentials officials - three U.S. senators "who daily and persistently threatened secretaries and volunteers who would not give them other people's credentials."

Reeves is at his best in these kinds of situations.The way he limns William vanden Heuvel is typical: "Intelligent and charming, vanden Heuvel was an exaggerated political type: the coat holder. He had never made it on his own but, loyal and possessed by demons of self-promotion, he had stayed close to a series of powerful men - working his way through General William ('Wild Bill') Donovan . . . Senator Jacob Javits, Governor Averell Harriman, and the Kennedys, John and Robert. Then in the days of 1975, when Carter could, get no one else, vanden Heuvel became the Georgian's man in New York. Before the convention vanden Heuvel was getting 200 calls a day. "The thing you have to know about me is that I'm not a political person, winning was never my bottom line - I went for Carter in 1975 because I though he'd make a good President,' vanden Heuvel told an interviewer without mentioning that he had run, and lost, for governor, congressman and Manhattan district attorney."

What doesn't work well, for my taste, is Reeves's attempt to drag the sleazier side of New York's fleshpots and streetwalkers into the convention orbit. He flashes back and forth from political scenes to a strip joint or a conversation with a tired hooker. We learn how many tricks are turned, and for what price, and in the face of what problems. So what? So it sells, I suppose - or is supposed to. Neither do you get from Reeves's book any sharp sense of Carter and his key people. But, then, that isn't his primary focus.

For all its imperfections, Kandy Stroud's look at "Jimmy" does dive a faithful rendering of the long trek to the White House. It's a serious effort, and an honest one. The problem is tedious construction, mechanical pace, and embarrassing prose.

Judge for yourself.Kandy on Jimmy: "He was a changeling who matured late. He was once a young man whose dreams were only of the seas and of self, a military man who built weapons of war and destruction, whose eys were finally opened to the needs of others.But he relinquished his career on the water and thrust himself into the tilling of earth. And the seeds of his Christian faith, which had fallen on fallow ground, flowered as did his spirit and concern for others. In the land he found himself and his purpose. He directed his search for power to the service of mankind."

And then Moses cam down from the mountain, and spake thus to the people . . . At least, she doesn't use the uppercase "He."

In fairness, Stroud's portrait of Carter does have its fascinating sides. When she describes her personal reactions to him or encounters witnessed at first hand, we get perhaps as good insights as we have had into his contradictory personality.

Stroud offers other intriguing personal glimpses, showing Carter sullen, kind, angry, thoughtful. Her characterization of Carter's staff is arresting. Some of the people around the candidate fell into the liberal, polished, gentlemanly camp. But the others were, in her terms, "hardly what one expected to find surrounding the Christo-centric candidate. It was composed in large part of men who embodied qualities almost entirely opposite to their leader's. One member of the inner sanctum described them as a 'morally degenerate, corrupt staff.' Thy placed less of an emphasis on candor than Carter. ('Jimmy won't lie to you, but I will,' said one.) They lusted after other women with more than their heart. ('What's a campaign about but screwing and drinking, anyway?' another told me.) They were irreligious, undisciplined, arrogant, disorganized, rowdy and nonideological . . ."

You get the picture. So what?So they're in the White House now. Whether they will find religion, morality, purpose serving Jimmy and the people are all parts of stories yet to be told. And you can bet they'll be told, and retold, imperfectly or otherwise, by journalists. Journalists who write books, that is.