This is the biography of a giant generation -- the 76.4 million people who were born in the fiesta of fertility from 1946 to 1964. The American birth rate, like that of other industrialized countries, had declined steadily for 200 years. It is now declining again. There was a single, unprecedented aberration -- the phenomenon we call the baby boom. Every social and economic issue facing the nation today has a population dimension -- which is often a baby-boom dimension. The "boom" has had a profound impact on the United States in the past quarter-century. Given the sheer weight of its numbers, the future of this generation will be the story of the rest of our lives.

The central premise of the book is that the size of a generation determines its fate. Landon Jones, former Time education editor and now a senior editor at People magazine, denies that demography is destiny. Yet he appears to accept uncritically the idea that great numbers inevitably bring competition with one's peers, and that the "great expectations" of the boom generation will be thwarted by its own crowding. This thesis was developed by economist Richard Easterlin, and is presented here in lively style, backed up by scholarly research and mind-reeling strings of numbers.

Crowded maternity wards, double shifts in kindergarten, trailers for emergency classrooms, uncertified teachers -- these are some of the life experiences of the boomers to date. But like a pig in a python, as this group moves through the passages of life, the crowding will continue. Already the boomers are encountering brutal competition and frustration as too many of them try to squeeze into the limited jobs available. Their demand for affluence and an emotionally fulfilling "life style" will inevitably, says Jones, be thwarted by their own numbers. They can expect crises in Social Security and the possibility that there may be more people collecting pensions than are working. At the end, there may be no room in the cemeteries.

The boom stands out because it was both preceded and followed by generations that were much smaller. The small numbers of the group raised during the Depression lessened competition. Some demographers called this the "good-times generation," and Jones says they "saw summer sunlight move through their lives." They had a favorable lifetime experience that promoted optimism and therefore fertility. These were the parents who moved to the suburban split-levels, who had easy credit for second cars and boats for their vacations. Jones calls this postwar period the "Big Barbecue," "a feast spread out for an entire nation, and everyone scrambling for it." It was this euphoria, as much as anything, which stimulated the procreation ethic.

The domination of the boom generation they produced was so complete it amounted, says Jones, to a "tyranny of teen" -- a virtual crisis of socialization, as cultural institutions tried to civilize "the invasion of the barbarians." We feared a breakdown in family life, symbolized by lowered SAT scores, a drug subculture, and a steep increase in VD and teen-age pregnancies -- all orchestrated to rock music -- "the soundtrack in the movie of their lives." Jones says that some fears were phoney: the crime wave of the '60s was largely a fraud. Since most violent crimes are committed by teen-agers and young adults, what seemed like a breakdown in law and order was simply the boomers passing through. Similarly, while race riots, assassinations and Vietnam traumatized this generation, their very numbers made the war tolerable. We were able to fight the longest war in our history using only 6 percent of the draft eligible young men.

They grew to adulthood in a period of virtually uninterrupted prosperity -- the biggest, richest and best-educated generation ever. They are also the first television generation, having spent one-quarter of their waking lives -- more than in classrooms or with parents -- at the electronic hearth. By age 21, the average boomer will have been bombarded with as many as 300,000 commercial messages.

Given the leap in the number of working mothers and the casual acceptance of day-care centers, they may also be the last generation to be reared by housewives. They made the '50s a child-oriented society, and turned the '60s into a time of stormy adolescence. Along the way, this generation has forced us to change the way we think about work, women, divorce and parenting.

This is first-rate social history -- journalism with data, sociology minus the jargon. Jones assumes straight-line conclusions based on aggregate statistics, and his technique is anecdotal rather than scientific. Nonetheless, this is a full-length portrait of America 1946-80, and seems likely to take its place alongside Vance Packard's "The Status Seekers" and "The Hidden Persuaders," David Riesman's "The Lonely Crowd" and William Whyte's "The Organization Man."

It's an extraordinarily numerous generation -- a baby boom whose numbers may also be their tragic limitation. They've been center-stage all their lives: War Babies. Spock Babies. Sputnik Generation. Pepsi Generation. Woodstock Nation. Now Generation. Love Generation. Protest Generation. Me Generation. Perhaps they even were the impetus for President Carter's "national malaise" speech. This generation is still young, and their biography remains unfinished. As the Chinese say, we have the misfortune to live in interesting times.