An absorbing, you-are-there account of bad days in Boston: the city's violence-racked busing experiment, as experienced by three families--one Irish Catholic, one black, one Brahmin. Lukas refrains from taking sides in one of the 1970s' most controversial issues; rather, like a good ex-New York Times man, he gives us just the facts. Dramatic facts they are. In June 1974, US District Court Judge Arthur Garrity found the school system unconstitutionally segregated, and ordered a hastily-devised busing plan into effect that fall. But Boston, colonial cradle of liberty, was a city ""divided into ethnic enclaves, jealously guarded turfs where intruders of other nationalities, much less different races, were not welcome."" Opening day--and many days after that--saw boycotts and brawls, rocks thrown at schoolbuses and students frisked for weapons. Common Ground traces the reactions of each family in alternating chapters. To the McGoffs of working-class-and-proud-of-it Charlestown, the bused-in blacks are trespassing aliens; the widow McGoff marches in demonstrations of the local anti-busing group and daughter Lisa leads school walk-outs and sit-ins. Among her protests' targets: two daughters of welfare-dependent Rachel Twymon, who's raising six kids alone in a new and already crumbling Roxbury project. Meanwhile, the liberal-minded Divers settle in the South End, one of Boston's few interracial neighborhoods, where their two boys attend a progressive, integrated school. But the community spirit disintegrates under a mounting crime wave, and finally the Divers flee (not without mixed emotions) to a suburban house, complete with picket fence ""rearing its ivory spine against the world,"" Interspersed with their stories are chapters on key public figures: Mayor Kevin White, Cardinal Humberto Medeiros, School Committee Chairwoman Louise Day Hicks. Though masterful mini-histories of Boston political and social institutions (probably written with an eye to excerpt), these sections interrupt the dramatic drive of the family sagas--clumsy intrusions of ""the larger picture,"" as if Lukas didn't think the ordinary people were interesting enough to carry the book. And tracing everyone's ancestry back to colonial days is purely self-indulgent padding; the nearly 700-page tome doesn't even get into Judge Garrity's order until one-third of the way through. But stick with it: despite the shaky structure, Common Ground reads like a living novel.