THE SOVIET REGIME is in its seventh decade of power and during that long career of tyranny has accumulated many enemies. None has done it more damage than Alexander Solzhenitsyn, and that must be a source of grim satisfaction to him. Among the Russians themselves there is a pronounced uneasiness that their greatest writer since Tolstoy has rejected the system, in principle and in all its manifestations, as morally insupportable. He has done more than that: he has brought to its condemnation a manner of writing so powerful, and a use of words so incandescent, as to match the scale of the gigantic crimes he exposes. The horrors of the Soviet Union and the writings of Solzhenitsyn will remain inseparable, so that long after the regime is destroyed and buried, his words will press down on it like an admonitory tombstone. Would that Nazi Germany had thrown up so devastating a literary prosecutor!

Solzhenitsyn's impact on the Soviet image abroad has been even more important. In the United States his work played a critical part in halting, then reversing, the left-leaning liberalism which was so characteristic of the early and mid-'70s. He helped to give intellectual substance and passion to the emerging counter-revolution. But in France, whose intelligentsia for so long contrived to make the barren rigidities of Soviet communism palatable in the West, Solzhenitsyn changed the whole course of intellectual history. He played a paramount role in destroying the appeal to youth not only of the Marxism-Leninism practiced in the Soviet world but of Marxism itself. The recent demographic collapse of the Communist Party, for so long the most stable feature of French politics, is in great part his work.

The biographical truth about a writer of such influence is clearly of enormous importance, and Michael Scammell, a translator of Dostoevski and Tolstoy and founder and former editor of the Index on Censorship, cannot be accused of treating it lightly. His book which is, of necessity, only a preliminary study, is nonetheless 1,050 pages. He has faced immense difficulties in establishing the facts. The obstacles are not merely the lack of access to Soviet archives and the active hostility of the authorities, but the almost paranoid suspiciousness of the subject himself. Those in the publishing world who consider Solzhenitsyn the greatest living writer admit he is also the most angular. He originally gave Scammell's project his blessing (though it is in no sense an official biography) and collaborated in the work; then he withdrew his approval, and from start to finish he was a hard man from whom to extract information. Scammell refers to "the stubborness, truculence and distrustfulness of the labor-camp veteran," but the fierce hostility Solzhenitsyn capriciously directs towards admirers does not spring wholly from his past ordeals.

It is the obverse of his genius and it springs from the intense precision of his vision of the truth. He will accept no ifs or buts or qualifications; he is not a "reasonable" man (no more was Tolstoy). But those who find him impossible ruefully admit that it was his very intransigence and stiff-necked obstinacy which gave him the courage to defy Soviet power. When the irresistible force of the KGB met this immovable object, it was the old curmudgeon who won the battle.

Scammell understands all this and his approach to Solzhenitsyn's character is well judged. He treats him as a great, but mortal, man. As a rule he spares us intrusive comment and allows the facts to speak for themselves. Of course the facts are often in dispute, but Scammell has done his best to test the authenticity of Solzhenitsyn's often suspect autobiographical writings and get at the truth behind the mendacious propaganda put out by the Soviets, notably the doctored version they published of his first wife's memoirs: here, Scammell was lucky to have her unsolicited help. He takes a lot of trouble, too, to give the background to the painful episodes in which former friends of the writer were induced or duped by the KGB into denouncing him. The result is a very long book but it is never prolix and I do not see how it can have been substantially shortened.

As we would expect with such a great artist, the urge to write came very early. In a sense, Solzhenitsyn was a writer in 1928, when he was only 10, and much of the material for August 1914 was already in written form when he was 18. It is important to grasp two salient factors in his intellectual formation, both well brought out in Scammell's account. The first is that he came from the oppressed class of the Czarist gentry, persecuted and discriminated against by Leninist policy. There is nothing he does not know about poverty, degradation, cold and hunger, and in the person of his mother, raised in great affluence then condemned to a life of endless drudgery which she bore with stoicism and dignity, he was presented with an image of redemption through suffering. All these early experiences were to resurface later, and shape the contours of his traditionalist Christianity.

Despite the cruelty and corruption of the regime, to which he was a horrified witness as a boy, Solzhenitsyn's youthful phase of ideological idealism took (perhaps inevitably) the form of an intense devotion to Marxism-Leninism. It is important to grasp that he is not a congenital opponent of collectivism but a convert from its meretricious charms. He never worshipped at the icon of Stalin -- quite the contrary -- but he believed in Lenin, and his revulsion to the Stalinism of the '30s took the form of a desire to return to the pristine Leninist truth. It was precisely this longing to create a new party embodying Leninist virtue, discussed in letters to a friend, which led to his arrest and imprisonment, after a successful wartime army career, in 1944.

Solzhenitsyn's eight years in the Gulag, and a further three in exile, erased the Leninism, restored him to his past, matured him as a writer by giving him an overwhelming purpose in life -- the exposure, down to the minutest detail, of a monstrous system of evil -- and turned him into a complex personality combining great moral authority with rage, hatred and pettiness. Those who ponder the problem of evil and of theodicy might reflect that only the Gulag could have produced art of such scope and passion. Among the major writers of our time, he is the most closely linked to his experience. By his laborious efforts, Scammell has produced the best guide so far to this tragic figure and the somber world his books have thrust upon us.