Davis, a cultural anthropologist, calls the past 100 years of Mexican immigration to the US the ""greatest movement of a people in human times."" Here, through dozens of interviews, she fashions an informal history that puts a human face on an international phenomenon often viewed primarily in economical terms. Studies and statistics, says Davis, do not begin to explain the astonishing annual migration of five million people. ""Politicians, academics, and bureaucrats"" tell ""whichever story fit [s] their purpose."" Here, the workers tell their individual tales. Some cross the border only once and remain or return to Mexico forever, finding the US not to their liking; others make the often dangerous trip repeatedly for decades. For many young males, the journey has become a ""rite of passage."" Almost all come for seasonal work on the farms and ranches: backbreaking, menial, minimum-wage work, but far better than the $3.35 per day they would earn at home. Many are in the US illegally--wetbacks-- but ""the truth is we don't take any jobs that Americans would want because they can collect more from welfare."" From the Deportation Act of 1929 to ""Operation Wetback"" in 1954 and the Immigration and Naturalization Act of 1965, government policy about Mexican immigration has fluctuated with the economic times. The Reform and Control Act of 1986 gave legal resident status to nearly three million immigrants and penalizes employers who knowingly hire ""illegals."" The long-term effect of the controversial bill is uncertain, says Davis, but for the Mexicans coming into the country, guided by often unscrupulous ""coyotes,"" the crossing remains perilous: ""To cross is to die a little."" A notable, serious study that gives voice to a frequently tragic past and an uncertain future.