The pursuit, capture, trial, escape, and re-capture of a teenage murderer--in a long novel that wavers between two genres: half of the time it's a painstakingly detailed documentary; half of the time it's an old-fashioned revenge-melodrama. The elderly parents of N.Y.C. cop Steve Kornienko are knifed to death on 7th St. one night. So, though Steve is ordered to stay clear of the case, he does his own sleuthing--which leads to 15-year-old Johnny Blanton, a.k.a. ""Quick,"" a blond-haired, angel-faced animal whom we see in action (thieving, killing) and at home (Mom's a sexy drunk, brother Paul's a studious good-kid, sister Cindy's a midtown hooker). Johnny is caught. He confesses. But--in the novel's best, most documentary-like section--the cops have difficulty making their case; Johnny gets a hot-shot public defender; he ends up pleading guilty to a manslaughter charge, with a short sentence to be administered by the Family Court. And then Johnny escapes--which means that the story now returns more or less to Steve, who (already angry about the reduced charge) vengefully trails Johnny to hooker Cindy's place. . . and nearly kills him: ""he wanted to do it with his hands. His hands! His hands!"" Cohen (330 Park, The Taking of Gary Feldman) does a solid job with the police and trial procedures here. But his portrait of the ""angel face"" killer isn't especially convincing, and the uncertain focus throughout (with limp subplots galore) makes this awfully slow going: too talky and diffuse to work as a vengeance-thriller, too thinly contrived to score as a gritty slice-of-life.