Another exceptionally clever detective story by the masterful PD (does it stand for pure delight?) James, who celebrated her 85th birthday with the publication of this 13th book featuring Scotland Yard's Commander Adam Dalgliesh. Set on an island off Cornwell -- where you can almost hear the crashing of waves and the taste of the salt air -- an unpleasant and famous novelist is bizarrely murdered. It's the classic whodunit, deftly handled.  (GBR604, $14.95)