An absorbing look at the complicated, ever-changing institution of marriage. New Yorker staff writer Harris (Holy Days, not reviewed) brings a journalist's eye for detail and a graceful style to this account of four very different married couples who had one thing in common from the start: ``Nothing in their premarital thoughts had in the least prepared them for the reality of wedded life.'' The first couple, well-to-do, illustrates at nearly every turn the received wisdom that much marital difficulty revolves around moneywith the refreshing twist that in this instance it is the husband who (in his wife's words) ``had no sense of budget, and no sense of constraint.'' Harris's second case study, a working-class couple, struggles to survive without much education and without much money, dissolving and reuniting, reassuring themselves that ``things weren't so bad,'' trying as best they can to make do in an uneasy world. The third, and most interesting, couple is middle- class and African-American, each partner blessed with a long view and a keenly developed, sometimes ironic sense of the way things work: ``The hippie phenomenon fascinated [the husband]. He was amazed that young white kids could check out of the system, then casually check back in three or four years later. . . . Black kids, he says, could never behave like that.'' The final couple, bohemian with a studied vengeance, has matured gracefully through the era of open marriage to a conception of life as something other than a playground. Harris pretends to no grand theory, and she is pleasingly candid, as when she admits to a certain surprise at the one element that her subjects share in their daily lives: ``Everyone worked terribly hard all the time, and . . . rarely got a chance to come up for air.'' Despite such burdens, Harris's four married couples endure through better and worse, making this a useful survival manual for newlyweds.