Titans of the Junkyard : THE TAX INSPECTOR, <i> By Peter Carey (Alfred A. Knopf: $22; 279 pp.)</i>

Three generations of Catchprices run a failing General Motors dealership in the slummy outskirts of Sydney, Australia. Frieda, the octogenarian matriarch, interferes, sulks and carries gelignite in her pockets as another woman might carry Mace. Cathy, her husky daughter, runs the business end but belts out country-and-Western ballads, and yearns for stardom. Her brother, Mort, a mild, hairy man, runs the shop while dreaming of a quiet little garage of his own. Jack, the other brother, has broken away to become a rich downtown developer.

As for the grandchildren, Mort’s sons: Vish is a Hare Krishna, but keeps getting dragged into the family’s stormy councils; 16-year-old Benjamin, glittering and deranged, has a prophetic determination to turn the crumbling business into a dazzling money-spinner.

But it is not simply an eccentric family that Peter Carey has created in “The Tax Inspector.” The Catchprices are a race of ramshackle Titans, the Gods’ doomed predecessors. Monstrous, deformed and often very funny, they threaten to pull in anyone who comes near their collapsing universe.

Maria Takis doesn’t simply come near; she marches right in. She is the tax inspector of the title, and when she drives up to Catchprice Motors one day and asks for the books, she brings the whole structure of family secrets, madnesses and wild improvisations crashing down quite as surely as if she’d ignited the explosives in Grandmother Catchprice’s pockets.

Before the end, the gelignite will, in fact, be set off. By that time, the Grand Guignol will seem almost an anticlimax, so spectacular have been the schemes and confrontations that Carey has introduced.

“The Tax Inspector,” written with considerable brilliance, is not so much a novel as a modern mythology. Its larger-than-life figures--the Catchprices and,-less obviously, Maria--suggest personifications for the unmanageable forces at loose in the world. Unlike the old mythologies, here it is not a matter of thunderbolts, sea-storms and other threats of an unmastered Nature, but rather the different and equally unmanageable threats of a world where Nature is mastered, and the masters are disintegrating.

All the principal characters follow vehement and often nutty purposes, only to be yanked oppositely by equally odd and vehement cross-purposes. When Maria arrives, she is all business and evidently prepared to sink the whole disreputable Catchprice enterprise. But it is not so simple.

For one thing, she is eight months’ pregnant. Her impregnator is Alastair, her boss. He is a charismatic idealist; he sees tax collection as a noble mission. It is the means by which the disgusting profits of land speculators and money artists will be channeled into schools and old-people’s homes. Maria, along with her colleagues, is inflamed by the vision. Her immigrant mother was abused all her life by arrogant bosses; now Maria can make them pay.

Alastair, however, is a skunk as well as an idealist. Maria’s condition irritates him. In order to pressure her into quitting, he assigns her such dead-end tasks as going after the Catchprices. They may be crooked, but they are clearly no profiteers. The dealership, economically speaking, is a junkyard.

So Maria’s sense of mission is undermined from the start. And the Catchprice strategy--masterminded by Benny--to show her their human side undermines her further. Eventually, while attempting to conduct her auditing by day, she breaks into the tax office at night to try to cancel the Catchprice file out of the computer.

The original tip, after all, was lodged by Frieda, who is convinced that Cathy and her husband are stealing money to launch her singing career. And all the Catchprices behave in equally unsettling ways. Mort, who wants to get away, urges Maria to find evidence of fraud. Cathy arrives at Maria’s house late one night, toting her guitar, and tears off a ballad. If they are fined, she urges, she will never be able to get away to sing.

The highly flavored brawl of Catchprice manias through which Maria wanders has a fearful line of force running through it. Frieda contributed one part of it. Her outsized energy and a fanatical determination snagged her a quiet, music-loving husband, Cacka, and then put together, first a chicken farm, and then the dealership for him to run until his death.

Cacka’s own contribution was a curse. He sexually abused both Cathy and Mort as children. Mort, in turn, abused Benny as a baby. Coming upon the scene, Mort’s wife shot him and missed; the bullet hit Benny, leaving a blue scar on his shoulder.

It is like the mark of Cain. Benny is the gleaming, driven end-product of his family heritage of zeal and perversity. He dyes his hair blond, shaves his body, buys a gleaming white suit and a set of self-actualization tapes, proclaims himself the Angel of Plagues, Ice and Lightning. Angelically, he tries to pursue his mad vision of turning the decrepit business into a model of capitalism on hallucinogens, a car agency that will make millions not by the sale of cars but by pyramiding credit and insurance rake-offs on the side. He doesn’t manage to get started or sell a single car; instead, he turns his blazing urgency on his family, or takes it to the dank basement where he has built a machine to inflict abusive sex.

There are all manner of side excursions, notably a love affair between Maria and Jack, the only Catchprice who seems to have escaped the family vortex. It is tender, sensual and, since Maria is eight months’ pregnant, astonishing. But gradually, the book centers on a confrontation between Benny and Maria. The contenders take on archetypal configurations: Maria as a type of struggling humanity, and Benny as humanity transformed by pride into the fallen angel, Lucifer. The end is grisly.

Carey is powerfully good at creating his odd Titans, and his success accounts for the book’s excitement and allure. He is not nearly as good at giving a sense of what they stand for, or of linking them to the mythology he is trying to suggest. This may account for a queasy feeling of letdown, of intoxication followed by hangover. In fiction, to be alive can be just about enough; to be larger-than-life, you need a purpose.