NORTH OF MONTANA

NORTH OF MONTANA April Smith (Knopf, $23) Los Angeles FBI agent Ana Grey may not be the most brilliant crime-thriller heroine to come along, but she's certainly one of the most captivating. In her robust debut-which succeeds on the strength of its irreverent but not invulnerable star-Smith submerges the actual crime in a narrative tangle of FBI interoffice politics, Hollywood publicity-mongering, and unsavory family secrets. The rabidly ambitious and perpetually horny Grey is assigned to investigate accusations of drug trafficking that a legendary movie star levels against a popular young orthopedic surgeon (who just happens to have employed a recently murdered Salvadoran immigrant who claimed to be a cousin of Ana's). Well-paced and believable, the action leads up to an unresolved ending that has ''keep an eye out for the sequel'' stamped all over it. That's just fine. We look forward to running into Ana Grey again. A -Rhonda Johnson