Cast your mind back to a time before "The Thorn Birds," before the label "saga" was slapped on every book that dared an exotic locale, or touched down on more than one continent, or addressed the concerns of more than two or three blood relations. For it is "Kabul's" chief virtue that it is the genuine article -- the fully imagined, closely researched, energetically written story fixed in a distinctive place and time.

The block of amber offered for our inspection is Afghanistan in the period from 1973 to 1979, under the three regimes (one a monarchy, one nominally republican and one Marxist) that preceded the Soviet "Christmas Invasion." Suspended there is the half-Afghan, half-American family of Omar Anwari, minister in the king's cabinet, pillar of Kabul society, product of "the blood of fifty generations of Pashtun mountain tribesmen."

Because Omar was educated in America and married a Bostonian, the three Anwari children are also sent to school abroad: the eldest, Mangal, to the Sorbonne in the '60s; the daughter, Saira, to Radcliffe; and the luckless youngest son, Tor, to Moscow. Each member of this generation is thus situated to express some aspect of Afghanistan's plight as a punching bag, or of the tension between its semifeudal, Islamic character and the forces that would modernize it.

Alerting us early that it is going to give good political weight, "Kabul" is slow to start. Helpfully, these Anwaris are a contentious bunch. Just as Omar is tendering an honorable resignation from the king's cabinet over corruption in the royal household, Mangal is enlisting in the bloodless coup that will take power the next day. Saira, choosing exile in New York over the Islamic conservatism that would constrict the life of an unmarried woman in Kabul, carries on a love-hate relationship with her family and the country of her birth. Her love relationship is with a Russian colleague at the United Nations -- an occasion for her to learn, as her feminism might have told her, that the personal is political.

Tor alone is apolitical. He might be expected to join the progeny of other former potentates among the Eurotrash, were he not such an angry young man that at the outset he's sentenced by his parents to a Moscow education. There, in the novel's very best scenes, he is redeemed by his love affair with another student, a British girl involved with Soviet dissidents.

In the course of "Kabul," the Anwaris transact all the venerable business of their fictional kind -- breeding, falling in love, undergoing political epiphany, fleeing, dying and (once) even trying a hand at resurrection. That they do it in unpredictable, sometimes enthralling ways is a testament to first novelist Hirsh's talent: It's rare to find such a large cast that numbers not a single lazily drawn character or -- perhaps the largest pitfall, given the book's ambitions -- political sandwich board among its members.

But eventually, with the exception of Tor, his lover and his mother, the relative realism of the Anwaris makes them relatively tiresome. Too much of the plot hinges on family rancor. There is not only the rancor that explodes in one early scene, setting off a chain of circumstance that will dominate the Anwaris' lives, but also a quietly continuous, talky rancor that causes the characters again to make the decisions that will do them least credit, and their family and country most harm.

By the time the Soviets are massing at the border, they seem almost to be a particularly virulent expression of sibling rivalry.

A little more than half of "Kabul" is set in Afghanistan, and the novel's other great flaw is that these scenes are the least successful. They clearly contain as much love as research, but they're not nearly as absorbing as the accounts of Tor in Moscow or of his sister in New York. Here again, politics is one of the culprits. Conscious of our feeble apprehension of Afghan affairs, the author has written a brief "note" at the beginning of the book summarizing the history she is about to dramatize, but the concession stops there: Throughout the book, rigorous lessons in factionalism are explicated in dialogue -- a form that tells us more than we want to know, because it dramatizes less than we'd like to see.

Still, "Kabul" is well worth the trip. It's inconsistently dramatic, but it's never hard to pick up, and often hard to put down. To speak in the terms of its own milieu, may it live long.