FICTION

STREGA by Andrew Vachss (Knopf: $18.95; 293 pp.). It’s getting tough to tell the good guys from the bad guys in crime fiction, and lawyer/author Andrew Vachss doesn’t help matters any in “Strega.” Burke, the avenging angel of Vachss’ gritty first novel, “Flood,” returns here to match wits with the low end of the criminal spectrum: child molesters. A tightly wound ex-con, whose concept of justice falls only slightly to the left of vigilantism, Burke leads his private army--including a mute Mongolian ninja , a prostitute of indeterminate sex, a Nazi-hunting junkyard owner and a huge Neapolitan mastiff--on missions of mayhem to rid Gotham of some truly scummy evil-doers.

In “Strega,” a ravishing Mafia princess hires Burke to find the dirtballs who forced her 6-year-old nephew to pose for a pornographic picture and convince them to hand over the photograph. The boy is deeply scarred, but it is hoped that some of his trauma would be eased by destroying the photograph. The search for the pornographers takes the reader on a Cook’s tour of New York’s seamy underbelly and a psychological journey through Burke’s back pages.

What drives the novel is Burke’s ferocious need to see his brand of justice served and Vachss’ many compelling insights into criminality. (He obviously has drawn from the many sex-and child-abuse cases he’s handled.) It also helps that his repertory company of cagey crime fighters is perfectly suited for a city where the law of the jungle has become the law of the land--and where the sheep, our children, are so much at the mercy of society’s wolves.