BELOVED By Toni Morrison Knopf. 275 pp. $18.95

IT SEEMS somehow both constricting and inadequate to describe Toni Morrison as the country's preeminent black novelist, since in both gifts and accomplishments she transcends categorization, yet the characterization is inescapable not merely because it is true but because the very nature of Morrison's work dictates it. Not merely has black American life been the central preoccupation of her five novels -- The Bluest Eye, Sula, Song of Solomon, Tar Baby and, now, Beloved -- but as she has matured she has concentrated on distilling all of black experience into her books; quite purposefully, it seems, she is striving not for the particular but for the universal.

There could scarcely be more vivid evidence of Morrison's ambition than Beloved, which attempts nothing less than to depict, within the life of one woman, the entirety of slavery and its aftereffects. The novel is set in Ohio in the post-Civil War years, with frequent flashbacks to the antebellum period in Kentucky, Georgia and other slave states; it is the result of conscientious research and, as is always true in Morrison's work, of deep moral and social convictions. That it is also beautifully written doubtless needs no elaboration; Morrison is a prose stylist of prodigious powers, and in Beloved she has resisted the allure of excess to which in the past she has occasionally succumbed.

For these and other reasons Beloved is a work of genuine force, and it occupies moral territory so high as to be unassailable; but viewed purely as a work of fiction it has serious shortcomings, none of which is easy to discuss without seeming to belittle Morrison's real and important accomplishments. What it boils down to is that Beloved -- like Tar Baby and, to a lesser degree, Song of Solomon -- is diminished by the very ambition that distinguishes it. As what William Styron once called a "meditation on history" it is superb, and several of the scenes recreating the brutality of slavery are quite breathtaking; but it is a novel in which themes are more important than people, with the predictable consequence that the people never really come to life.

Its central character, and the one who comes closest to full development, is a former slave named Sethe. Now in her mid-30s and living in semi-rural Ohio, she escaped from slavery in Kentucky 18 years ago after a terrible beating by white men. En route to Ohio she gave birth to her fourth child, a daughter, and had a blissful month of freedom upon reaching her mother-in-law's house. Then a posse of whites flushed her out and, empowered by the Fugitive Slave Act, attempted to return her and her children to Kentucky; the result of this awful confrontation was the death of her elder daughter and her family's isolation within the small black community that once had offered it shelter and support.

The precise details of her daughter's death are revealed slowly and hesitantly, but from the outset it clearly is the trauma around which everything else revolves; all preceding events point directly to it, and all ensuing ones directly from it. But if it is the principal reason why Sethe believes "the future was a matter of keeping the past at bay," it is hardly the only one. Life under slavery, the mysterious disappearance of her husband, the dangerous journey to freedom, the stories she hears from others about the suppression and torture of blacks: all contribute to the sense of desperation and suspiciousness with which Sethe views her situation, and to her deep doubt that she can ever lead a normal life.

It is in her depiction of Sethe's life under slavery that Morrison is at her most subtle and ingenious. Had she chosen to take the Harriet Beecher Stowe route, replete with cruel masters and noble slaves, it would have come as no surprise; arousing readers' anger against a cruel system is easy when the cruelty is made as offensive as possible. Instead, though, Morrison has chosen to set Sethe's slave years at "Sweet Home," a farm in Kentucky where the owner and his wife go beyond the bounds of kindness -- where the five young male slaves "were believed and trusted, but most of all they were listened to," where the women were treated with respect and "nobody, but nobody, knocked her down," where something approximating friendship existed between master and slave.

In Sethe's mind Sweet Home borders on the idyllic, at least as it was until the master's death and his replacement by a schoolteacher who substituted stringency for kindness and quickly turned what had seemed to be heaven into another version of hell. But as Sethe begins to awaken to the reality of slavery, she comes to understand that no matter what form it takes, it is still slavery. Garner, the former master, may have been kind, but: "Everything rested on Garner being alive. Without his life each of theirs fell to pieces. Now ain't that slavery or what is it?" Whether the master is cruel or kind he is still the master, with utter control over all conditions of his slaves' lives; on no level is the system susceptible either to apology or to sentimentalization.

WHICH IS WHY, in a novel in which death is a dominant image, Morrison argues that there is something even worse than death. Sethe, brooding about her daughter's murder, visualizes it: "That anybody white could take your whole self for anything that came to mind. Not just work, kill, or maim you, but dirty you. Dirty you so bad you forgot who you were and couldn't think it up." Thus at its heart Beloved is not so much a novel about the loss of life as about the loss of self, the denial of identity and worth that is the highest price slavery exacts.

This struggle to regain her true self, to shield it against the invasions of others, is what most engages Sethe. She fights it in many ways, most of all in her relationships with the mysterious young woman named Beloved, who appears to her one day and who may just be her daughter reborn, "the true-to-life presence of the baby that had kept her company most of her life"; with her surviving daughter, Denver, a "charmed child" who eventually offers her mother a degree of salvation; and with Paul D, a former slave from Sweet Home who offers her love and the prospect that "we can make a life."

These relationships are convincing enough as devices for thematic exposition, but rather less so as genuine human connections. Because the characters so obviously exist in order to represent certain experiences and points of view, few of them sufficiently engage our interest and sympathy. Beloved is written with great and affecting passion, yet it touches the mind more than it does the heart. It achieves thematic grandeur, but falls short of full humanity. ::