IF the test of a good book is that it somehow makes us better able to understand ourselves, then the latest recounting of Chile's 16-year travail under the iron-fisted military regime of Gen. Augusto Pinochet Ugarte is sure to be judged first-rate."A Nation of Enemies: Chile Under Pinochet" is the story of how a country with a 150-year democratic tradition does a turnabout to welcome the violent military overthrow of its elected government. Reaching beyond a mere recounting of life under an all-powerful military, the book dissects the reasons why dictatorship appealed to so many Chileans - even in a society with strong democratic proclivities. Boston Globe Latin America reporter Pamela Constable and Georgetown University Professor Arturo Valenzuela manage to layer - like a multilevel chess board - the actions and motives of the Army, the dictator, the secret police, and the technocrats, showing their impact on individuals, families, and children. Yet, the strength of the book is not so much its careful organization and documentation of a very complex scene, but its ability to expose the essentially mental nature of dictatorship with its roots in extreme societal fear and hatred. The military coup that killed leftist President Salvadore Allende Gossens in Santiago on Sept. 11, 1973, ended quickly. The process of subduing a populace educated in the democratic tradition began immediately afterward. "If you walked on the grass, they would blow whistles at you. But people didn't resist; they complained among themselves, but they obeyed. That's how it happens.... You accept things little by little, and finally you end up submitted to them." That is how Josiane Bonnefoy, a Chilean student, described to Constable life on a college campus not long after General Pinochet's military began to assert control over every aspect of life in an effort to "purify" it of socialist or communist tendencies. Civilians, as well as key players, explain their sense of how Chile became ensnared in a fascist system, imparting to readers why ordinary people - perhaps even readers - might under a certain climate of fear do things they would never otherwise consider. Near the end of a chapter entitled "The Culture of Fear," the authors quote a villager who says simply that "Fear was a sickness we all caught." A page later, the authors reinforce how fear can be contagious in society and illustrate its frequently destructive effect on moral self-government. "I worry more about the fascist within than the fascist without," says Marco Antonio de la Parra. An ordinary Chilean, Mr. de la Parra recounts his belief that it was evasion of moral choice that made dictatorship possible. "How many of us could become torturers? Pinochet could not have happened if the society were not already sick." There are eerie parallels between Chile's experience and Nazi Germany's. One example is the Chilean Army, which was trained by Prussian advisers starting in 1885, laying the foundation for an elitism that disdained civilian authority. "Only in my fatherland have I seen the equal of Chilean soldiers," remarked the German ambassador to Chile in 1910 as he watched Chilean cadets goose-step through Santiago. Interestingly, Pinochet and his officers frequently referred to Chile as the "fatherland." Under Pinochet, Chile also had its own internal security force - the DINA - whose methods apparently differed little from Hitler's Gestapo. This organization was mostly responsible for creating an atmosphere of fear and mistrust in society as it burrowed relentlessly in search of communists and leftist sympathizers. Perhaps one of the greatest ironies for South America and Chile is that this country has today the most vibrant, free-market economy on the continent. It is a system created, however, by force and designed by the University of Chicago-trained economists who advised Pinochet. Yet even this step of progress, because of the way it was implemented, came at a high cost to many Chileans. "What has happened to this country? I used to be so proud to live in a democracy, and now I feel my honor and dignity have been violated," lamented a taxi driver after racing past a confrontation between riot police and student protesters. "There is such malignancy, such power. Dictatorships put people to sleep, and the only ones brave enough to fight it are the youth. Today, I am ashamed to be a Chilean." Ultimately, as we know, the nation's long democratic tradition reasserted itself with young people leading the way. Pinochet was beaten in a remarkable national referendum in October 1988. In March 1990, Patricio Aylwin Azocar was inaugurated, the first civilian president since Allende. On Oct. 14, Chile's Supreme Court decided to try two of DINA's former chiefs in civilian rather than military courts, a move hailed by human-rights reformers. Gen. Manuel Contreras and Col. Pedro Espinoza are charged with ordering the assassination of Pinochet critic Orlando Letelier, who was killed along with his American assistant Ronni Moffit in a 1976 car bombing in Washington, D.C. "Our aim," the authors write in the preface, "was not to polemicize the plight of a relatively small number of Chileans - perhaps tens of thousands - who suffered from direct political repression. It was ... to understand how members of an educated Western elite had discarded the civic values they had once mythologized ... and how 42 percent of the country could vote for an aging dictator in 1988." Pinochet, who in his 70s still presides over Chile's Army, has left what appears to be a lasting wariness in Chileans. "We became used to being in the cuckoo's nest, and we couldn't escape," said Marco Antonia de la Parra. "The fear has lessened now, but how little would it take to bring it back?"