MISSUS By Ruth Park St. Martin's. 247 pp. $15.95 THE HARP IN THE SOUTH By Ruth Park St. Martin's. 225 pp. $16.95 POOR MAN'S ORANGE By Ruth Park St. Martin's. 274 pp. $16.95

THE HILLS," begins Ruth Park's The Harp in the South, "are all full of Irish people." The hills in question are the tenement-encrusted dips and rises of Sydney's Shanty Town, the slum district of Surry Hills. The time is, more or less, the 1930s. The "Irish people" are largely represented by one family, the Darcys -- immigrants and the children of immigrants -- although there are plenty of compatriotic nuns and priests and neighbors to fill out Park's vivid, sentimental portrait of the Irish experience in early 20th century Australia.

The Harp in the South, the story of Hughie and Mumma Darcy and their daughters Roie and Dolour, was originally published in 1948, to be followed a year later by Poor Man's Orange (published in the United States as 12 1/2 Plymouth Street) which traces the family's fortunes into the 1940s. Both novels became international best sellers at the time, although they have long been unavailable in the U.S.

In 1985 Ruth Park unexpectedly transformed this popular pair into a trilogy with a new novel, Missus, which jumps back in time to the years between the turn of the century and the beginning of the Depression, portraying Hughie's and Mumma's parents, childhoods, affairs and courtship in the Australian country town of Trafalgar, worlds away from the cramped squalor of Surry Hills. Missus was published in the U.S. in early 1987 and is now being followed up by reissues of the two original novels.

These chronological details would not be worth mentioning except for the fact that Missus is so different in style and sensibility that readers who enjoy it might very well be disappointed by its two sequels, and vice versa. The Harp in the South and Poor Man's Orange are done in a style at once realistic and naive, long on energetically rendered character portraits and minutely detailed depictions of daily slum life and short on social consciousness, despite their working-class setting. Missus, by contrast, is a more abstract, tougher work, stripped of sentimentality and suffused instead with a bitter modern feminism.

The very title of the new novel is an ironic slap at the institution of marriage which is celebrated so fulsomely in the earlier books. " 'If you're a woman,' " thinks Margaret (soon to become Mumma) " 'in the end someone always arranges your life for you.' " By Poor Man's Orange, an aging Mumma, scarcely capable of conscious reflection, knows only "that marriage, the sacrament, was more important than the people committed to it." Yet it is an interesting question which of these positions represents the maturer view.

From the outset Missus refuses to pull its punches, preaching passionately the theme of women cheated and short-changed. "A nervous understanding came to {the child Hugh} that {his mother}, too, must have begun life as a preparation for something wonderful. But all she got was a shanty for a home, constant illness, and two boys, one a cripple and one always in mischief."

Hugh's mother finally drowns herself in a creek. The other women in the novel -- with the sparkling exception of Margaret's mother, Eny -- do not thus violently self-destruct but all, in their different ways, see their lives leach away into servitude and defeat. Park does not dispute the possibility of a mutually enriching marriage -- the novel provides one or two luminous examples -- but for most, women in particular, it is little better than "a lightless, confined space."

The Harp in the South carries on the story of Margaret, who becomes Hugh Darcy's "missus"; the portrait of their marriage is at the center of the larger mural the novel paints of between-wars Surry Hills. Poor Man's Orange continues on another generation, gradually zeroing in on Dolour, the youngest of Mumma's and Hughie's children.

As Missus and Mumma, Margaret has changed from a buxom beauty into a down-at-heels slattern and the little flickerings of spirit or hope or outrage she had shown as a girl are much closer to being extinguished. Hughie is a feckless drunk; their only son, 6-year-old Thady, disappears from the street one day and never returns; the family lives hand to mouth in conditions of unspeakable squalor and dreariness (people in general seem to suffer far greater physical deprivation in these urban slums than they do in the rural towns of Missus). Much later Roie, the angelic daughter, dies in childbirth and Dolour, the clever one, is forced to leave school through ill-health.

And yet Ruth Park seems determined to include in her portrayal of these foul rag-and-bone shops of the heart just as many ladders as she can find or invent. Unlike Missus, both novels are deliberate paeans to the human spirit and to the non-feminist virtues of faith and endurance. Sometimes the result is very nearly maudlin. The story of Roie's idyllic marriage to part-aboriginal Charlie Rothe, for example, must have caused even Ruth Park herself, in later years, a twinge of embarrassment: "Charlie was the centre of her world. She ran to meet him at night, always with the same delight. In bed she lay behind the wall of his back, feeling little and protected and secure, as a woman of the caves might have felt long ago, as she lay with her man shielding her from the cave opening and the great darkness and mystery beyond it." The Harp in the South ends with Mumma actually telling Hughie, that selfish old boozer, "how lucky we are."

But sometimes, too, the result is genuinely moving, through the agencies of either pity or a grim kind of comedy. Grandma's fight with Hughie over who is to make the Christmas pudding; a virtuoso passage on bed-bugs; the lonely suicide of Patrick Diamond, the Darcys's cancer-stricken lodger; Mumma's hastily aborted visit to the dentist; a glimpse into the bittersweet inner life of the local nuns; the hilarity and torture of Dolour's adolescence ("an extraordinary kiss, like a clout from a damp hairbrush, landed on her lips"); the whole unbearably sad affair of the lost child, Thady: all these become instances of Ruth Park's typically Irish understanding that (as Leopold Bloom has it) "In the midst of death we are in life. Both ends meet."

Missus, disillusioned and ironic, is by far the more sophisticated novel, but The Harp in the South and Poor Man's Orange keep their own unfashionable charm. If at times they stumble from the inspirational to the bathetic, it is still refreshing to meet an author willing to run such risks in her representation of real feeling and real (that is, hard-won) hope.

Elizabeth Ward writes frequently about modern Australian fiction.