OVER THIRTY YEARS AFTER its publication, Fort Apache: New York's Most Violent Precinct remains the definitive account of the vicious cycle of violence that has griped urban America over the past century. A swollen head floating down the Bronx River, a junkie murdered for stealing a woman's wig, a French Connection-style chase through blind alleys, police barricaded inside their precinct as a wild mob lays siege to the station - and, above all, mindless violence that seemed to erupt in profusion for no apparent reason against the cops who faithfully served and cared deeply about the neighborhood that was rapidly imploding.