Fall of '82, it seems, is going to be a big season for history-lesson novels. But while such writers as Clive Irving (Palestine) and Peter Driscoll (Algeria) have managed to blend fact and fiction with respectable, informative results, Grey's 800-page chronicle of Vietnam, 1925-1975, turns rich, complex history into a contrived, soap-operatic family saga--heavy on coincidental meetings, doomed romance, illegitimate babies, and long-lost children. In the 1920s, teenager Joseph Sherman visits Vietnam with his hunting US Senator father, immediately reacting against colonial injustices as he meets: French official Devraux (who sleeps with Joseph's mother); the native-aristocratic, collaborateur Tran family; and Devraux servant Ngo Van Loc, a secretly revolutionary peasant. So, over the decades, Sherman (and kin) will return to Saigon again and again--always getting fatefully involved with these three other clans. In 1936 he'll come as a scholar, fall in hopeless love with Tran daughter Lan (who's betrothed to young Devraux), and make contact with much-tortured guerrilla Loc--whose wife and son have died for the nationalist cause. During WW II pilot Sherman will be shot down over Indochina, winding up in the care of Lan's in-law Dao Van Lat--a fanatic, European-educated rebel who introduces Sherman to the charismatic Ho Chi Minh (a wartime ally against the Japanese): Ho later dupes OSS-man Sherman into helping to legitimate his end-of-war coup; Sherman learns that Lan bore his child, Tuyet (they rescue her from rural famine); Sherman rails against the postwar restoration of colonialism in the south. (""It's a goddamned betrayal of everything Western democracy is supposed to stand for!"") In 1954 journalist Sherman is on hand for Dien Bien Phu--and the killing of Lan's husband Devraux by Loc's son Ngo Van Dong (Lan will die too, alas). Then, from the 1960s on, other Shermans appear in Vietnam with near-comic regularity: Joseph's kid brother Guy is a Saigon CIA agent who'll tacitly abet the Nhu coup and die in a grenade clinch with yet another Ngo-family rebel; soldier-son Gary will die trying to prevent My Lai-style excesses by his comrades; soldier-son Mark will be a POW (who happens to be in the custody of Lan's brother Kim!); daughter Tuyet will become a Viet Cong killer. And in 1975, after writing ""the bible of the antiwar movement,"" Sherman will head for Vietnam one last time--to rescue his grand-daughter. Grey, author of the compelling A Room in Peking and two undistinguished thrillers, does surround these melodramatic, implausibly patterned episodes with lots of historical/political/military detail: speeches by Ho, battles, tortures, debates, coups. And the exotic atmospherics are competently handled. But the nearly all-male cast--especially those vanilla-flavored Shermans--is colorless; the prose is serviceable at best, often descending into the pulp-romantic or amateurishly expository. And the penny-dreadful plotting, along with the preachily obvious Message-waving, makes this a mega-saga for the undiscriminating only--especially since so much fine, serious fiction has come out of Saigon's more recent decades.