THE WILL AND LAST TESTAMENT OF CONSTANCE COBBLE

Constance Cobble--a 50-year-old widow with an ""accidentally"" killed husband somewhat mistily in her background--writes detective stories on the Caribbean isle of St. Martin. And, while Constance broods and dallies with the isle's American community (especially Jerry Tosca, a retired ventriloquist with yet another of those eerily human dummies), she works on her latest mystery novel: all about the drowning death of seductive scuba-diving teacher Bootsie Baker, a femme fatale who has fatally attracted the husband-and-wife owners of a St. Martin boutique. An initially intriguing novel-within-a-novel setup--but the gimmick soon becomes irritating and self-defeating: the fictional mystery never grabs, and it steals time and focus from Constance's own real-life, darkening developments--she marries Jerry (for vague, ominous reasons), and their mutual hatred leads to a murderous, ironic denouement, Constance deserves a novel all to herself, and though veteran Forbes does entertaining page-by-page things with the tricky premise here, it's a half-satisfying diversion; not to be sneezed at, but--considering what Forbes can do at her best--not fully up to snuff.