Ex-Policewoman Dorothy Uhnak who has featured another attractive one, Christie Opara, in her novels of procedural suspense, now tells a tri-generational, somewhat thickset story about the New York City police force culminating with a vaguely Knapp-like inquiry as to whether it should be able to handle its own. . . corruption. The original Sergeant O'Malley was slashed to death -- with the worst indignity of all -- by the black whore he lusted after, but was buried as a hero and remained one to his son, also Brian, next in line. Brian is rigid and hard and has his own brutal/ sensual instincts to contend with (particularly the first girl who hooked him while she kept herself alive on her back) and never learned the truth about the father he tried to live up to until it was almost too late. And this is finally shafted home by his son Patrick after he returns, embittered, from Vietnam. The O'Malleys have none of the lovable ugliness of those other new centurions who wear their heart on the sleeve while stretching out their palm under some table -- in fact they're encased in all kinds of prejudices beside their uniforms, even when they take them off. But you're expected to respect their bullnecked limitations and dedication to law and order which Miss Uhnak has well staked out from parish to precinct. Even if she hasn't managed to get the lead out of their feet. Still the book is a ""full selection"" of the literary Guild and may do as well as predicted.