A CHANGE OF CLIMATE.<i> By Hilary Mantel</i> .<i> Henry Holt: 322 pp., $12 paper</i> : EIGHT MONTHS ON GHAZZAH STREET.<i> By Hilary Mantel</i> .<i> Henry Holt: 278 pp., $12 paper</i>

Two-thirds of the way through “A Change of Climate,” James, the head of a hostel for “derelicts and drunks” in the East End of London, is shaken to his Christian core. He has just received a letter from his nephew Ralph, who is a missionary in Botswana. Something terrible has happened to Ralph and his wife, Anna, something unimaginably violent. And because James is wise, kind and an old hand at life’s tragedies, he tries to compose, haltingly, a few words of encouragement in preparation for Ralph and Anna’s return to England.

“There is nothing, there is nothing worse, there is nothing so burdensome . . . there is nothing so appallingly hard . . . as the business of being human. . . .” The inadequate words die in his throat as he catches sight of himself in a mirror on the wall, a “desiccated old man, worn by humility, sucked dry by the constant effort of belief.” Quickly, he shies away from these unbearable truths by submerging himself in altruism. “Glass is a danger in a place like this,” he thinks, where fights break out in the blink of an eye and everything is a potential weapon, and he “should take the mirror down.”

It’s one of the more chilling moments in this darkly humorous book (perhaps Hilary Mantel’s best), encapsulating the push and pull between emotion and repression, self-sacrifice and self-deception, pragmatism and confusion, goodness and evil--in fact, all the complicated “business of being human”--that animates everything Mantel writes.

Ranging widely in subject matter from family conflicts to the dilemmas of modern Roman Catholic prelates, from the French Revolution to English expatriate life, Mantel’s seven novels offer lessons in life’s contrariness, in the tensions between free will, unfortunate accident and involuntary behavior. Thus a well-meaning but disappointed mother inflicts emotional damage on her daughter, while a good priest causes someone’s death. Philanthropists bring succor to the world but neglect their own children; colonized Africans cause as much damage as their vicious masters.

In Mantel’s world, a wolf lurks inside every cottage, or as Anna puts it in “A Change of Climate”: “In safety, there is danger. In tears, the awful slicing comic edge. In moments of kindness and laughter, the murderer’s fist at the door.”

Even those chilled by the persistent downbeat of Mantel’s vision will surely be seduced by her sharp humor, reminiscent of Muriel Spark or Edna O’Brien, and her nail-biting narration in which ambiguous political and religious concerns are wrapped in the brisk plotting of a suspense thriller, a la Graham Greene or Brian Moore. (What is it about writers with a Roman Catholic background--Mantel was convent-educated in Northern England--that they seem to have a special knack for combining powerful narrative with philosophical speculation and humor?)

This blend of dark and light, comedy and tragedy, heart-in-the-mouth narrative and a slow-working analysis of the human condition, is nowhere more successfully displayed than in “Eight Months on Ghazzah Street” and “A Change of Climate.” They are Mantel’s third and sixth novels respectively (published in England in 1988 and 1994), now available in the United States, along with Mantel’s most recent novel, “An Experiment in Love” (1995), published here last year to critical acclaim. Also available is “A Place of Greater Safety,” a powerful historical novel about the French Revolution.

“Eight Months on Ghazzah Street” and “A Change of Climate” are aptly paired for their American debut. Each describes the tribulations of a young British couple who live respectively in Saudi Arabia and Africa. (Mantel lived with her geologist husband in Botswana for five years and in Saudi Arabia for four before returning to England in 1987). Both couples, though basically well-meaning, are motivated by selfish reasons: one to make money off the Saudi oil boom, the other out of an apparent missionary zeal that really covers the urge to escape domineering parents. A Western sense of entitlement to the blessings of liberty makes them ill-equipped to understand cultures more authoritarian than their own, and their thoughtless naivete is ultimately their downfall.

“A Change of Climate” weaves back and forth between the terrible past in Africa and the dreary present in Norfolk, England, where Ralph Eldred has inherited the family charitable trust whereby the couple continue their good works among the English rural poor, often taking depressed homemakers and drug-addicted teenagers into their own home when there is no room for them elsewhere. Bit by bit, we learn of the tragedy that beset Ralph and Anna in Africa and that they have kept secret from their four children “in the service of the great god Self-Control.” Instead, they teach their children that there are only “Good Souls and Sad Cases,” that the world has “no wickedness in it.”

Clearly this is a lie. From self-evasion to outright dishonesty, from kindness unmitigated by an awareness of malice to silence about the past, Mantel suggests that secrets of every sort can only warp our lives. Upon his return to England, Ralph (who has little intuition about people, only an instinct to help them) has a rare epiphany. Burying the past inside himself, he realizes, makes it “more potent,” not less. “No bad action goes away. Evil is energy, and perpetuates itself; only its form changes.”

But Mantel also suggests we have choices. In a double-edged crisis, in which Anna discovers Ralph’s late-blooming love affair while a drug-addicted teenager staying in their house runs amok, there is the hint of possible healing in their lives: of real goodness, not just the numbed “professional Christian” sort by which they had been living, but genuine tenderness based on real feeling. Only in revelation (and that includes self-examination), Mantel suggests, can the rot of secrecy and self-deception be rooted out and a more honest life begin.

Revelation doesn’t help the couple in “Eight Months on Ghazzah Street,” however. In fact, the secrets uncovered here only make life worse, or nightmarishly reveal further secrets that can never quite be pinned down.

Andrew Shore has accepted an assignment as an engineer on a new building in rapidly growing Jeddah. His wife, Frances, joins him, only to find that her life in this country will be severely circumscribed; she can barely leave the flat they have rented without being harassed by leering Arabs who resent her unveiled appearance. “This is a private society,” she discovers. When one door closes, another slams shut.

Frances’ sense of estrangement is further embodied by her inability to find her way around (though she is a cartographer by trade), for this is a place where, in a frenzy of development, buildings disappear, roads change course, and even the coastline shifts as more land is reclaimed from the sea, a process that symbolizes, for outsiders, this alien country’s ungraspable nature.

Not all is doom and gloom, however. Frances is a woman of some spirit. Her thoughts on the repressive Saudi life and the smug expatriate scene are bitingly satirical, culminating in one painfully funny section, a dinner party at which Frances’ newly purchased nonstick pans deposit black flakes of “Saudiflon” all over the food, to the accompaniment of racist and sexist remarks by her patronizing British guests. (The two American guests are more sensitive.)

Nevertheless, she finds herself sinking into despair and lethargy, obsessed by occasional noises she hears in the empty flat above. As it turns out, the sounds are not simply the product of her paranoia but of genuine clandestine activity. As Frances makes further discoveries about the flat, the Shores’ lives become endangered. The depressing message--”leave alone what you don’t understand because the gaps between cultures can never be bridged”--is almost the opposite of the message relayed in “A Change of Climate.”

Though all Mantel’s novels illumine societal evils--be it the British class system in “An Experiment in Love,” the malevolent interplay between personality and public events in “A Place of Greater Safety” or colonialism in “A Change of Climate”--”Eight Months on Ghazzah Street” is perhaps Mantel’s most overtly political work. Her outrage against a society that virtually imprisons women, mutilates thieves, stones adulterers and disappears over-curious intruders is palpable. Both Arabs and Brits are hit hard for embracing greed and corruption, in such a sweeping indictment of unfettered capitalism, that the reader can’t help but wonder if Mantel’s guiding philosophy is that of the Boer doctor in “A Change of Climate” who says: “We’re all barbarians.”

Yet even though the blinkered British expatriates in “Eight Months on Ghazzah Street” remain boxed in by xenophobic claustrophobia until the bitter end, and the altruists of “A Change of Climate” gain only the minutest grasp of the human state, Mantel is rarely dogmatic. Rather, she suggests, life is as murky as Frances Shore’s state of mind as she grapples with the vagaries of Saudi culture. In more optimistic moments, she tells us that life’s truths are sometimes perceptible.

Ralph Eldred, on the verge of leaving Anna (at her request), wonders whether to pack a fossil, a Gryphaea or “Devil’s Toenail,” a souvenir from childhood, because cataloging old stones gave him confidence in “the order of the world.” Now he sees that the past is indeed as petrified as this ancient remnant. What’s mutable is how we see it.

Ralph takes the fossil, a symbol of his childhood dreams for a happy life, but also, perhaps, a devilish token of the long-lived claw of unhappiness in his heart, and throws it into the wastepaper basket. Experience, Mantel suggests, may open up new layers of meaning, yet it never really provides an answer.