IT IS A COMMONPLACE to say of serious writers that they have only one tale to tell, and they write it again and again. But the mind of Nadine Gordimer has a reach so wide, that each of her books, indeed each of her short stories, seem to be new ground, freshly observed. Nadine Gordimer is a white South African writer, and her one tale over 30 years concerns the strains and passions of the morally serious, educated, humane, white minority-within-a-minority as it tries to deal with, or ignore, or defeat its bizarre and ugly historical inheritance. This is, of course, the oppression and degradation of the immense black majority.

It is not precisely true that every one of her themes rings a change on the liberal conscience. There are stories of childhood, of sexual passion, of mothers and sons, glimpses of daily life which have a surprisingly up-to-date American quality. The sexual revolution, feminism, the fragmentation of personalities, of families, the brooding violence, are familiar to us, as well as shopping centers, drugs, "garage boutiques" and junk food. The critical difference between the best of Nadine Gordimer's people and us, however, is that they live in a beloved country which is constitutionally unjust, whereas we are only shabby or inept in the implementation of laws that are overall just. And the consequence may be, as it is in the latest of her fine novels, July's People, that one may break under the sheer strain of being an understanding person, of extending one's understanding of the variables in these late 20th-century events beyond what can be borne.

July's People is the novel that follows Burger's Daughter, that comprehensive and perhaps too relentless exposition of the situation in South Africa today, and the perfect birthday present for Secretary of State Haig. Rosa Burger passes a quite solid childhood with swimming pool and cook-outs in a passionately dedicated Communist family, its devotion to black liberation bringing them severaly to prison and death. Exhausted by this childhood, Rosa lives the first years of her adult life in some suspension, but in the end she is at peace, and Burger's daughter.

Maureen Smales, in July's People, will succumb to that exhaustion. The novel opens in the imminent present when the revolution breaks out in South Africa, and the Smales family, Bam, Maureen and their three small children hidden in the family camper, escape to at least temporary safety in their servant's homeland. The Smales have always known that the revolution was inevitable and "had given the time left as ten years, then another five years, then as perhaps projected, shifted away into their children's time. They yearned for there to be no time left at all, while there still was. They sickened at the appalling thought that they might find they had lived out their whole lives as they were, born white pariah dogs in a black continent."

July is the name the Smales had long since given to their servant of 15 years, a man they love and (quite properly) trust, who is allowed to visit his own family once every two years, but whose family is not allowed to come to live with him in white Johannesburg. And as the bombs are dropping and the fires are breaking out, it is July who directs the Smales in their camper, sometimes walking ahead over stubble and through creeks in the dark, to his people. "July knew the whole six hundred kilometres, had walked it, making a fire to keep the lions away at night when his path bordered and even passed through the Kruger Park, the first time he came to the city to look for work."

The Smales are given the hut of July's old mother in the little impoverished tribal village. The blacks are decent, skeptical; they circuit around this time very alien presence and continue their timeless ways. The whites are decent, grateful, do their own washing, cook their own mealie-meal and wait. The days go by, and the staticky transistor sometimes picks up news of bombing and continued battle. There is no way they can think through to a future. There is no imaginable rescue. From whom? By whome? "Would we go back?" They had fled the fighting in the streets, the danger for their children, the necessity to defend their lives in the name of ideals they didn't share, in a destroyed white society they didn't believe in." Maureen and Bam are left with too little to discuss, and they retreat into an unpleasant, uncompanionable silence.

Bam is a relatively uncomplicated, civilized man, an architect "back there," and frightened though he is, he presides over events as best as can be done. Maureen, however, has a quick, conflicted passionate self, unsuspected, or at leasat unreleased, "back there." She's drawn by an earthy sensual excitement to July, to July's people, the women in their huts -- "she did not know whether or not she was welcome where they dipped in and out all day from dark to light like swallows." Above all it is her position in regard to July that obsesses her, sending her into a whirl of contradiction. With their situations now dramatically reversed, she'd driven alternately to attract him, and diminish him, to test her power and to treat him with dignity and justice. It is July now who has the authority, about which he is casual and often amusing. Unexpectedly he disappears with the camper, an event extremely unsettling to Bam and Maureen, but returns with provisions for them.

In agitated relief Maureen says, "'Bam, we must pay July.' 'We'll pay. We'll pay. Did anyone see you -- I mean say anything? Ask questions? What's happening there?"

"He smiled and gave his customary high-pitched grunt of amusement and asked something obvious, to him. "Plenty people is know me. I'm from here since I'm born, isn't it? Everyone is greet me.'"

The confusion grows in Maureen's mind and outside it. July tells them that his chief has summoned them to an audience and their fears increase. But it seems all the chief wants if Bam's gun. Under the South African government there have been no guns in the homelands, and the chief is only interested in retaining his power. He is not concerned with revolution, black liberation, justice. July explains: "The African people is funny people. They don't want know this nation or this nation. The country people. Only his own nation we know, each one." But he dismisses the chief: "He's talking talking . . . He is chief but poor man, he hasn't got money. If they come over here, those what-you-call-it, the people from Soweto they bring them, they eat his mealies, they hungry, kill a cow -- what's he going to do? Can't do nothing. Talking, talking . . ."

The Smales fled that destroyed white society whose ideals they didn't share, to the bush, to July's people where their own ideals dissolve. It is difficult to honor sufficiently the subtlety, the understatement, with which this story and these characters are drawn. Day follows day, the tension tightens -- and without the almost obligatory set piece of murder or rape. July's People is among those seemingly slighter novels that become a benchmark in one's understanding, not only of South African realities, but of all good people in Western society, and how we buckle.