TALES FROM MAGARITAVILLE By Jimmy Buffett (Fawcett: $9.95) . Like his songs, Jimmy Buffett's short stories are lightweight, diverting and often funny. Most of the better stories are set in Heat Wave, a small town on Snake Bite Key. The pleasantly eccentric inhabitants of the fictional islet include Aurora and Bora Alice Porter, the twin sisters who run the local coffee shop, and writer/football coach Romeo Fleming, who keeps the eponymous iguana in "Off to See the Lizard." The wistful romances in "Take Another Road" and "Boomerang Love" suggest rum-soaked Tom Robbins stories, although Buffet lacks his flair for baroque traffic jams of adjectives. The weakest tales in the collection are the first-person narratives involving a singer-songwriter who bears a suspicious resemblance to Jimmy Buffet. The author's otherwise unpretentious style falters in these self-indulgent ego trips, and the stories sink into a morass of gurgling cutesiness. A good book to read on the plane en route to some sunny vacation spot--in search of that missing salt shaker.