Here, Eaker-Weil (a family therapist and frequent TV talk-show guest), with the help of health-writer Winter (The Scientific Case against Smoking, 1980, etc.), tackles a thorny problem that visits about 70% of married couples these days: infidelity. Though she cites statistics indicating that 35% of the marriages disrupted by this problem end in divorce, Eaker-Weil claims that only 2% of the couples she herself has treated fail to reconcile. The author's core thesis is that the tendency for infidelity is transgenerational--indeed, that in nine out of ten cases, there's unfaithfulness in the family trees of either the betrayer or the betrayed (causing individuals either to repeat inherited patterns of unfaithfulness or to seek out partners who are bound to betray them). Eaker-Weil urges both parties in a situation of infidelity to complete ``genograms'' that track down family penchants for unfaithfulness: She even serves up a chart of this kind for Prince Charles and Princess Di. The author also expresses great concern about how infidelity affects children, proposing that parents try play therapy to help their kids cope. But when Eaker- Weil gets down to what the man and woman directly involved should do, her prescriptions are narrow (``what concerns me most is the current argument that you can't be a liberated woman unless you fool around''); formulaic (``don't call a divorce lawyer''); or embarrassing (as in the case of the ``funeral game,'' in which traumatized spouses are supposed to enact each other's funeral rites). Meanwhile, the author overloads us with case studies bearing titles like ``Patty's Lost Paradise'' or ``Lars Confronts his Facade.'' Perhaps wise for its stress on transgenerational patterns, but too unsubtle to help people make sense of a problem that has infinite varieties and ramifications.