Baxt's recent mystery-comedies have tended to be more campy than witty--and so it is with this half-diverting concoction: an unabashedly contrived blend of Robert Louis Stevenson's The Wrong Box and Dame Agatha's And Then There Were None, with up-to-date psychosexual trimmings. Starting 40 years back, tycoon Andrew Graymoor and wife Helga (a pulp-romance writer) adopted ten children at intervals--raising them all on their private New England island. And now Andrew is dead from an accidental (?) fall, leaving his entire fortune in a ""tontine"": when all but one of the heirs dies, the survivor will inherit everything. So, when two of the younger Graymoors are murdered in Manhattan, the obvious suspects are the not-very-loving adoptive siblings, most of whom live in N.Y.C. Among them: an aging gigolo; an alcoholic lounge singer; a lawyer with S/M tendencies; a dumb-but-handsome Bloomingdale's clerk (with a greedy wife); spinster Martha, tending mother Helga back on the island; plus clothes designer Laura, married to her philandering ""brother"" Harvey, a well-to-do claims adjuster. More murders ensue, of course--both in Manhattan and on the island, where the whole clan eventually gathers for an isolated birthday/funeral weekend. Meanwhile, a dead body from the distant past surfaces--as do a clutch of financial/sexual secrets. And finally, with two cops and randy TV-interviewer Bella Wallace meddling as best they can, the psycho-culprit is uncovered. . . though another one may still be at large. Busy, predictable, and icily artificial--but the minor attractions here (bitchy repartee, a nastily ironic view of sex) should keep some readers faintly amused, mildly engaged.