Both halves of a happily married couple tangle with adultery over the Memorial Day weekend--in a sticky, awkward novel with a TV-movie tone and a crude, sentimental-melodrama finale. Ben Thorp is a Palo Alto lawyer, wife Claire is a technical writer; they're attractively 40-ish, very happy together. But when Claire flies off to visit boarding-school daughter Beth in N.Y., she's also flying off to a rendezvous with her secret younger lover Peter, author of ""four critically acclaimed novels."" And, while Claire spends the hotel weekend deciding to break up with the increasingly foul Peter (""Illusions, shattered like crockery, pierced her consciousness""), husband Ben back home whimsically bicycles down to Stanford in search of his first infidelity. Will he find it? Of course, and with instant cuteness: Ben bashes his arm in a biking crash, the ER doctor happens to be gorgeous Susan Delgado--so soon the two are walking the beach, riding a roller-coaster, and. . . ""She was soft, my God, but she was soft against him, wet and soft as summer rain."" Furthermore, the Ben/Susan fling seems to be more than just sex: wary Susan (experienced with married lovers) suggests a July 4th rendezvous; Ben gives her ""a slow steady smile that beamed light warmer than any sun in the heavens."" But then comes the news that the Thorps' college-son Mark is in critical condition after a Rhode Island auto accident! So both Ben and Claire rush to Providence--as feelings of guilt skyrocket and flashbacks romp through their earlier married days: ""So many wonderful moments with her children, so many crystal moments hung like translucent beads on a precious strand now threatening to break as she made her way through the dark New England night."" Ben talks to God. And when Mark does indeed pull through, Ben realizes that Susan's ""a flash in the pan,"" rediscovering his love for Claire: ""And as he entered her, as he came into the one place that was at once as familiar as nightfall and as astonishing as daybreak, he thought. . . ."" Well-meaning, perhaps--but dreadful.