The border between the United States and Mexico extends 1,951 miles.  Among the people who live along it are a migrant laborer huddled in a makeshift camp, a Chicano cowpuncher, a Pima Indian who makes his living tracking drug smugglers across the desert, and the millions crowded along the border in Mexicali.   In this beautifully written, unerringly insightful book, William Langewiesche allows us to see this boundary in all its political, moral, and emotional complexity.  Whether he is patrolling the border with officers of the U.S. Immigration Service or talking with the desperate men and women who cross it every day, Langewiesche is always engaged in what trackers call “cutting the sign” reading the marks that human beings have made on this contested land and decoding the meaning they hold for the rest of us.   ”Spellbinding. . . . The reportage [is] high art . . . for Langewiesche painstakingly uncovers the connections between elusive clues as he searches out the border and its people.”—Boston Globe