Americans extol motherhood as ""the most important job in the world,"" yet when couples divorce, mothers' and their children's standards of living usually decline precipitously, while fathers' rise. Crittenden, a former economics reporter for the New York Times, lays out the going rate for a woman's time: ""$150 an hour or more as a professional, $50 an hour or more in some businesses, $15 an hour or so as a teacher, $5 to $8 an hour as a day-care worker and zero as a mother."" Mothers (whose labor is not calculated in any official economic index) have no unemployment insurance to tide them over after divorce, no workers' compensation if they're injured and no Social Security benefits for the work they do, although a housekeeper or nanny paid for the same work would earn such benefits. In a breezy, journalistic style, Crittenden chronicles how the Industrial Revolution created the idea of the ""unproductive housewife,"" how this concept penalizes women after divorce and how tax policies encourage mothers to quit work. Crittenden proposes several remedies, some available in most industrialized countries (paid maternity leave, flexible work hours for parents, universal preschool, free health coverage for children) and others seemingly utopian (Social Security credits for mothering, remedying the tax bias against married working mothers). This thoroughly documented and incisive book is must reading for women contemplating parenthood or divorce, and could prove an organizing tool for women's organizations. Agent, Katinka Matson. (Feb. 15) Forecast: Bolstered by a seven-city tour to top markets, this is a great choice for women's reading groups, offering facts and figures that supplement recent investigations of the emotional terrain of motherhood, such as Susan Maushart's The Mask of Motherhood and Peggy Orenstein's Flux: Women on Sex, Work, Kids, Love, and Life in a Half-Changed World.