With the publication of ''At Canaan's Edge" -- the final volume in award-winning writer Taylor Branch's trilogy, ''America in the King Years" -- there should be no good excuse for the perennial substitution of myth for the far messier stuff of history. Numerous other writers, particularly David Garrow, Adam Fairclough, and Nick Kotz, have covered much of this ground before. But Branch's massive and deeply impressive study is bound to attract new and large audiences, and rightly so. Like the times he covers in these pages, the story he skillfully tells so well is unceasingly fascinating and dramatic.
And depressing. The years from 1965 to 1968 witnessed not only the persistence of substantial white violence against grass-roots black activists in the South but the outbreaks of white violence against activists who turned their attention to racial discrimination in the North as well. The federal government's protection of those on the front line of the struggle remained weak at best, fueling the radicalization of younger activists and the general disillusionment of many black urbanites. In retrospect, the changes effected by the 1964 and 1965 laws appear dramatic and substantive; at the time, for those suffering the continued taunts, assaults, arrests, and ''combat fatigue" associated with unending protests, the pace of change appeared glacial. Behind the scenes, the Federal Bureau of Investigation did everything it could to make life difficult for civil rights activists, refusing to take action against brutal Southern white police, declining to inform black leaders of real threats against them, spreading nasty stories (some true, many false) about key movement leaders to politicians and the press, and infiltrating and actively disrupting their efforts.