Trying On a New Life : A housewife ditches suburbia to discover who she is : LADDER OF YEARS, <i> By Anne Tyler (Alfred A. Knopf: $24; 336 pp.)</i>

Why does Delia Grinstead run away from her overbearing physician husband, her three sulky children and her depressive suburban life? With any of our realistic chroniclers of American middle-class life the answer would lie in the question. With Anne Tyler it lies there too, but the really interesting answer is: because her cat’s name is Vernon.

Tyler only seems to be a realist. It is true that in such novels as “The Accidental Tourist,” “Dinner at the Homesick Restaurant” and “Breathing Lessons,” her characters stumble out of the pages of the book, hang around, have supper with us, stay the night and never quite leave. Their lives are set on a prosaic chessboard: families, marriages, growing up and growing older, relinquishing choices and acquiring fantasies, and relinquishing the fantasies.

They move, though, not by straight lines but by a crookback hop and swivel, like tipsy chess knights. They move not by causes, effects and purposes but by accidents--accidents that in some hidden and exhilarating way they are prepared to incur, as one seemingly humdrum species of corn kernel is prepared to turn inside out and bloom white.

Thus in one sense, Delia Grinstead’s flight is entirely foreseeable. Tyler even announces it at the start, in the form of a small news clipping. It reports the disappearance, during a family beach holiday, of a Baltimore housewife, age 40, whose eyes are “blue or gray or possibly green,” and who “stands 5’2” or possibly 5’5” and weighs either 90 or 110 pounds” and who was wearing, her husband reports, “something pink or blue, either frilled or lacy or looking kind of baby-doll.”

So her family has only a hazy idea of what she looks like. For that matter, Delia hasn’t much idea herself. Sam, her husband, is bossy and matter-of-fact; her children, aged 15, 19 and 21, are oblivious unless dinner is late; her beloved father has recently died; and she has moved into and out of a comically embarrassing flirtation with a younger man. She picks up her answering-machine messages: Neighbors have invited them to dinner. She calls to accept but it turns out that the message is an old one and they’d gone there the previous week. “What kind of life was she living if every one of last week’s telephone calls could just as easily be this week’s?” she wonders.

Then one day, at the annual beach holiday--in a leaky cabin and with relatives packed grouchily together--Delia leaves the beach early and comes back to the cabin. When she calls the cat, a young man who is fixing the roof pops down; his name is Vernon, too. She has noticed his gleaming recreation vehicle parked outside, and she covets it as avidly as Toad coveted the painted caravan in “Wind in the Willows”: It means the open road.

Not quite deciding to, she cadges a ride. Before long they are driving down the Maryland shore and Vernon is nattering on about his family troubles. Young Lochinvar has turned kvetch, and Delia’s impulsive gesture dissolves into one more domestic assignment as sympathetic ear.

She hops off at a little town named Bay Borough. In the square she contemplates the comfortably seated statue of the town’s founder. “On this spot in August 1863,” the inscription reads, “George Pendle Bay, a Union soldier encamped overnight with this company, dreamed that a mighty angel appeared to him and said, ‘Ye are sitting in the barber’s chair of infinity,’ which he interpreted as instruction to absent himself from the remainder of the war.”

And so, still in her beach robe and with the week’s grocery money in her purse, Delia joins George in his absenting. She finds a rented room, buys some deliberately dowdy clothes and talks the town lawyer into hiring her as his secretary. She had worked for a Baltimore doctor, she explains, but--killing off Sam--he died. She settles down in the guise of a spinster seeking a new life; she makes friends and joins in such town traditions as watching the annual Bay Day softball game. Tyler, of course, does not provide a standard game. She sets it in an impenetrable fog through which Delia and her friends catch muffled shouts:

“Batter’s out.” “He’s what?” “He’s out.” “Where is the batter?” And, a beat or two later: “Who is the batter?”

“Ladder of Years” is the story of a fugue to change one’s life. It is told in Tyler’s characteristic manner, one that no other American writer approaches. Just as she subverts the domestic with fantasy--her situations are earthbound until you notice that they are gliding along two inches above the earth--she subverts fantasy with the domestic.

Delia’s new life is, in many ways, as dreamy and comically cluttered with tiny concerns as her old one. And the emotional clatter she had expected to get from her family amounts to an occasional irascible and oddly spaced burp. Her sister turns up after a week or two, talks vaguely about “stress” and leaves. The children are virtually silent. Sam fails to appear--Delia had been rehearsing her postures for the moment he should arrive--and finally sends a stiff note. It offers to discuss any complaints she may have but assures her that he “will not invade your privacy.”

The stiffness is undermined by two heavily inked outlines. Delia’s desire to flee across the border is undermined by the news that Sam will not invade. The arc of her escape is undermined by the gravitational force of her nature. Fugue turns to round. She quits the law office for a job as live-in homemaker to the local school principal, whose wife has walked out on him and their 12-year-old son. Delia replaces Delia; one set of family responsibilities replaces the other. The need to mother and to love is not easy to extirpate; a comically and tenderly drawn attraction trickles up between her and her employer.

In short, it has become a Tylerean logjam of decisions that add up to indecision and doors that slam latchlessly and bang open again. A number of loopy characters and situations zigzag their way through by the time a year has gone by, and Delia is summoned home to deal with her daughter’s wedding, gone chaotically askew. (Weddings are Tyler’s moments of truth, equivalent to Hemingway’s hunting and fishing exploits, though funnier.) It will force her to choose between Delia and Delia, between her new life and her old.

Tyler does not condemn her characters to stasis. She lets them move, though never as much as they think they are moving. She teaches them to blunder into the art of letting life subvert them.

Subversion--the parade that brings clowns, the clowns that bring a parade--is her art too, and the risk that goes with it. Pick up too many outriders, particularly if they are dedicated to slipping spokes in the wheel, and your vehicle slows. Momentum is Tyler’s difficulty; even in her best novels there are moments when vitality flags and things bog down. In “Ladder,” the bogging down can become especially onerous in the time between Delia’s flight and her return. A year is perhaps too long for what may or may not be--we only learn at the end--a round trip.