"I like nonfiction junk," writes Caryl Rivers, "the stuff that purports to be serious but is, at the center, marshmallow fluff." She is drawing a contrast between herself and her husband, Alan Lupo, who "likes reading the serious stuff, like government agency reports."

The trouble with this contrast is that it comes right after an article in the couple's book in which Alan has probed to the marshmallow fluff at the heart of a report from the General Accounting Office. One person's fluff is another person's gristle, no doubt. Still, there are plenty of other contrasts between the members of this odd couple. Alan is addicted to "The Baseball Encyclopedia," which gives the hard facts about more than 10,000 men who have earned money for playing a game. He dreams of baseball glory -- not megalomaniacal dreams of being a super-hero like Ted Williams, but moderate dreams of being Sid Gordon, who was simply "a damn fine ballplayer." mHer fantasies gravitate more toward the books of Frank Yerby. Comparing her fantasies with those in such books as "My Secret Garden," she is ashamed of them -- not because they are prurient but because they are not sufficiently imaginative.

Except for two children, Steven and Alyssas, "For Better, For Worse" is the first joint production of Rivers and Lupo, who have separately written four books: "Liberty's Chosen Home: The Politics of Violence in Boston," "Rites of Way: The Politics of Transportation in Boston and the U.S. City," "Beyond Sugar and Spice: How Women Grow, Learn and Thrive" and "Aphrodite at Mid-Century: Growing Up Female and Catholic in Postwar America." From the titles, you should be able to tell who wrote which.

"For Better, For Worse" is the first book either has written without a subtitle, probably because they could not agree on what it should be. He would have held out for something like "The Politics of Trying to Raise a Family on the Earnings of Two Moderately Successful Writers," while see might have preferred "Growing as a Family With Liberated Parents."

How they have managed to get together for a whole book -- let alone a family -- is something of a mystery. They are about as different as two human beings from the same society can be. Their differences are explored throughout the book and set forth succinctly in the foreword, apparently the only section of the book written jointly: "She ws a convent girl from the suburbs who kept her Catholic Youth Organization All-Star basketball jacket lovingly wrapped in tissue paper and who liked to commune with nature. He was a Jewish kid from the city who got separation anxiety when he got 500 yards away from concrete and whose idea of a sporting afternoon was a fast game of pool in a smoke-filled room."

Their book is a series of oblique dialogues -- generally disagreements -- on a variety of subjects that include health (Alan tends toward hypochondria; Caryl thinks a lot of germs are our friends); housekeeping (Alan is compulsively tidy; Caryl believes "dust balls are an act of God, not to be disturbed without filing an environmental impact statement"); and life in general. Alan, who is probably the one more given to abstract statements, sums it up neatly: "She cannot understand that nothing must be left to chance, that life must be well ordered and planned . And should there be any disruption of the planned order of things, then we must engage in crisis management."

Their articles alternate throughout the book, each pair presenting two sides of a particular subject and both of them frequently harking back to their shared experience as writers and as the parents of two vividly active children. Sometimes, they get awy from the family for a while and write about the government, best sellers, whither American society and that sort of thing. In these articles, the wit sometimes seems a bit forced, farfetched or not developed to its highest possible polish. But when they write about themselves, their home, their kids, their neighbors and pets and chronic problems, the effect is usually charming and sometimes hilarious.

There is often an air of barely controlled hysteria in Alan's voice when he talks about their family life, which is the main subject of the book. But there is also frequently a touch of desperate humor -- for example, when he discusses Jane, the family dog: "She sheds daily and at night. She has been shedding for seven years. She is seven years old. By now, she should have disappeared. You could take what this dog sheds and weave yourself a whole new dog."

As in their domestic life, Rivers and Lup share the workload for the book about equally. But on the whole, the book seems to be more in her style than his -- marshmallow fluff at the core. Perhaps this is becaise her approach seems, on the whole, more appropriate to the untidy, haphazard world in which we are sentenced to live.