FOR PLEASANT, undemanding entertainment, S. L. Sparling`s The Homing Instinct is hard to beat. The characters are peculiar enough to remain interesting, yet familiar enough not to strain credulity. The plot, while no challenge to the reader`s little grey cells, is carefully concocted and neatly resolved. The setting is the book`s strongest feature: Bloody Point, Maine, a coastal estate somewhat declined from its former glory and isolated on a peninsula jutting into the fierce Atlantic. The story revolves around a family a little more dysfunctional than average: James, the father, a kindly middle-aged doctor too much given to letting his patients pay in kind; his daughter Augusta, a dipsomaniacal an-anger of dried flowers; Singe, his selfish, irresponsible son, who has grown fabulously wealthy as an author of children`s books, but who ruins his life because he can`t get his 1,700-page novel published; Casey, Singe`s 14-year-old daughter, caretaker, and accountant; Lib, Singe`s erstwhile lover, arguably the most beautiful woman in the world and the flower-child earth-mother of his toddler son; and Leigh, a half-second-cousin-onceremoved of Augusta and Singe, who is a beautiful but irresponsible archaeologist. James, less than 20 years older than his children and Leigh, had an affair with Leigh in her nubile years. Now they resume the affair, she becomes pregnant, and, somewhat against her will, she agrees to have the baby, marry James, and let him raise the child. As part of their bargain, James lets Leigh excavate the meadow where some 20 Penobscot Indians were said to have been massacred before European settlement. But the bones Leigh digs up are not all old; she uncovers evidence of serious wrongdoing dating from the family`s rum-running days. `What will happen? The Homing Instinct casualty tells us what happens. Spatting could have heated up the suspense, thereby making the book a very original mystery story. Instead, she subjugates the mystery to the more humane aspects of the characters` attachment to home and family. But the characters are not well enough developed to carry this literary weight. James is entirely kind and naive, Augusta tipsy and cantankerous, Leigh cold and manipulative, Casey mature beyond her years, Lib loving and accepting, and Singe feckless. Given the family tree (laid out in a diagram at the front of the book), with its inter, laced generations of lust and hatred, The Homing Instinct could have been a richly woven popular novel. But the literary inclinations of the theme and the quasi-mystery plot pull in opposite directions against the book`s success as a family saga. In spite of its polymorphous architecture, however, The Homing Instinct has some unique situations and complications and a strong sense of place, and the writing is economical yet evocative. It will be a great book for the beach this summer.