THE NEW RUSSIANS, by Hedrick Smith, Random House, 621 pages, $24.95.

When Hedrick Smith wrote “The Russians” in 1975 the Soviet Union was a great, gray mystery.

The iron octopus of Leonid Brezhnev’s apparatus — Communist Party, government bureaucracy and military — effectively prevented the outside world from seeing the faces and stories of Soviet people. Only an insider, as Smith had become during his three years in Moscow for The New York Times, could bring those people alive for the rest of the world.

In 1991, the Soviet Union has let it all hang out — most of it, anyway. Soviets are glorying in the mess and confusion of Western-style politics, played out in the world press. Our view of the Soviet Union has expanded from Moscow to include places like Estonia and Azerbaijan, and dissenters vie with gray fedoras for international attention.

Smith has changed, too. No longer an insider, recording intimate conversation in a notebook, Smith is now a free-lancer who travels with a four-person television crew in tow.

Smith’s latest book, “The New Russians,” reflects all of that. It is grander, messier, more political and less intimate than “The Russians.” But if it is a different style of journalism, “The New Russians” is as helpful in figuring out the Soviet Union today as its predecessor was in its own day.

Oddly enough, even as daily events — the bloody crackdown in Lithuania, the frightening ascension of the military as a policy-maker throughout the union — race beyond Smith’s predictions, “The New Russians” rings true. Even where Smith has guessed wrong, he has set the stage so that today’s news seems almost inevitable.

Opening with 50 pages of background, “The New Russians” then breaks down the Soviet Union’s upheaval into four basic parts: glasnost, the liberating of speech and thought; perestroika, reform of the economic system; the national and ethnic struggles within the union, and the move toward democratic government.

That loose framework yokes together the stories of hundreds of people, from around the union and around the spectrum.

Smith first introduces readers to Tatyana Zaslavskaya, a closet sociologist in Siberia during the Brezhnev years, who played an important role in prompting reform. Her anvil-like honesty about the ailing Soviet economy shocked colleagues and impressed Mikhail Gorbachev. Smith tells her story, then lets her speak — a double salvo of insight, wrapped up in an intriguing character.

She is the first of many. People and ideas pore out at a dizzying pace, each one more impressive than the last.

Smith does not load the deck with reformers, either. He takes the reader to the living room of Nina Andreyeva, a chemistry teacher who became a hero for many when she began her campaign to end reform and bring back Stalinist control in the Soviet Union. Smith disagrees with her, but he lets her have her day in his book.

Many of his characters ultimately find themselves in the middle, unsure of how far they should go in embracing change. Igor Ivanovich Stroganov, the director of a mammoth industrial complex building more than $1 billion of heavy machinery each year, tells Smith that he understands the importance of market pricing and free trade with the West. But Smith points out that Stroganov feels much differently when it comes to giving his own managers freedom.

The central character of “The New Russians” is, of course, Mikhail Gorbachev. Smith devotes several chapters to his development, from an earnest schoolboy to a courageous student to a canny bureaucrat. He probes friends of the young Gorbachev to help us understand the Soviet leader’s independence, but he does not shy away from Gorbachev’s darker side — a hard and sometimes ruthless leader, a politician bred by the Communist system.

As a teen-age leader of the party’s youth organization, Gorbachev was not afraid to berate his girlfriend in public, then tell her in private that it was for the good of the party.

As a Politburo star, it appears that Gorbachev arranged to remove the life support systems of dying Secretary General Konstantin Chernenko at a time when Gorbachev’s opponents were spread across the country. In a few hours, what looked like a difficult Politburo battle became a shoo-in, and Gorbachev became the leader of the Soviet Union.

Smith’s affections for Gorbachev seem as fickle as the Soviet people’s, and as consuming. Frequently, Smith seems happy to put the blame for anti-reform tendencies on other forces in the Soviet hierarchy; but the author also admits that Gorbachev plays a mean game of Good Cop-Bad Cop. In the end, Smith is satisfied to leave the reader with that same ambivalence — it is an important part of the new Soviet Union.

“The New Russians” — like its subject — is a vast sprawling work. Smith’s clear and direct language makes it easy to pick up, while his loose structure over so great a distance sometimes makes it just as easy to put down.

But for those who stick with it, “The New Russians” offers a brighter light on what happened yesterday and a trail of clues to what will happen tomorrow.

Steve Kloehn is a feature writer on the NEWS style desk.