Tough Cookies : MIDNIGHT SWEETS <i> by Bette Pesetsky</i> ; <i> jacket illustration by Sandra Dionisi (Atheneum: $17.95; 224 pp.) </i>

Theodora, the protagonist of “Midnight Sweets,” tells her story in a succession of oblique feints. It is a cheerful story that comes out pretty well, but it has a lot of sadness in it, and a little awfulness.

Sadness is out of the question, though. Someone has declared it irrelevant. It is a third dimension in a two-dimensional world; a world of post-modern connections and disconnections.

To say: I am sad, I suffer, would be meaningless. It would mean that you disappeared. If the world is surfaces and facets, to go deep is to vanish.

Bette Pesetsky gives voices of discouraged buoyancy to people who must find tactics of deflection to tell you of their humanity. In this, she resembles Donald Barthelme. Three or four comical sentences succeed one another, each matter-of-fact in itself and seemingly devoid of much more than fancifulness.

It is in their juxtapositions that they resound. They have not grasped sorrow; they have--skipping, slithering--surrounded it.

Theodora, a prosperous entrepreneur--she makes designer cookies on a large scale--and an eccentrically successful mother of five children, has minor collapses from time to time. At one point, she feels disconnected from her left side. At another, she becomes unable to buy clothes.

She engages a shopper to choose for her, and she accepts the choices docilely. Except for jewelry; that she insists on picking out herself. And in a few sentences, ostensibly talking about necklaces, she gives us her deprived and painful childhood. It is worth quoting, as an example of how Pesetsky writes in seeming deafness so we can hear.

“I have a necklace made of rather nice wooden beads that my daughter Bonita made for me when she was five. That is one of the advantages of sending your child to a good school. When the children make something to take home--the ingredients used are of reasonable quality. The beads are oak and waxed to show the natural luster of the wood.

“Of course, Bonita’s gift to me is not a bit like the necklace I made. I have one shell left, and the paint still rubs off. My second-grade project. I brought the necklace home. Mother was in the house, perhaps with someone. Either they didn’t hear me or they didn’t want to open the door. I sat on a step and waited. In Leeward Elementary School I passed the test with a grade that the teacher said was too high.”

Theodora’s voice is funny, rueful and seemingly scatty. It is only bit by bit that we realize that this woman, who, as in Stevie Smith’s poem, seems to be “not waving but drowning,” has, in fact, patched driftwood together and is making precarious but purposeful headway.

We meet her in mid-babble. It is funny babble and there is a point to it, but for a while it is hard not to be suspicious of the way she has chosen to tell about her life. Where some mark off the leading events of their lives in terms of love affairs, or places lived in, her own benchmarks are cookies.

Childhood is the beginner’s ice box cookie. Her first marriage to a self-sufficient artist is evoked by the cookie named for him. The “Mortimer” is thin, elegant and topped with bitter chocolate. Her oldest daughter gets a sweet and sunny cookie. When Bonita becomes a teen-ager and more assertive, Theodora reduces the sugar to give it more bite. Bonita immediately phones hysterically from school. Altering her cookie is tantamount to disowning her.

And when Theodora comes to a bad patch in middle age--her second husband, as unfaithful as the first, has also left; all her friends seem to know about it, and one or two may not be entirely innocent--she inaugurates a series of movie-star cookies. Pola Negris are made of cherries in cognac, Laurence Olivier in “The Entertainer” is “a nut chunk with a slither of bitter chocolate.”

The device risks cuteness and crumbling. Pesetsky’s story does lapse from time to time into fancifulness. The continual skipping back and forth over her life’s chronology corresponds nicely to Theodora’s own difficulty in thinking about herself. But it tends to make the other people in the book--her husbands, friends and children--considerably less distinct, what with being fetched out and put back so arbitrarily.

But Theodora is fully the point; and Pesetsky’s maneuvers, for all their trickiness, turn out to be justified.

What we see, in fact, is a woman saving her life. Not triumphantly or inevitably, but through a quiet insistence on being herself, even when she doesn’t know who she is; and on refusing to let herself be crushed, even when refusal means danger.

Making cookies becomes much more than a whimsical image when we see a child whose mother hates her, and whose father, an amiable thief, comes and goes unpredictably. From the time a neighbor shows her how, Theodora takes up the study and practice of her skill as another prodigy--perhaps to effect a similar balance--might take up the violin.

When she is 15, even cookies won’t do. Her father walks out for the last time, leaving her and her helpless stepmother without money; for a while, Theodora becomes a burglar. Recalled in her fragmented, dispassionate voice, and without melodrama, the burglaries are comical and humane.

In one house, hearing a husband and wife quarreling, Theodora tells herself that their loss, when discovered, may bring them together. Discovering a disgustingly dirty kitchen in another house, Theodora scrubs it clean. She imagines the wife bringing her lover home, and the lover being put off by dirty faucets.

Here again, whimsy might threaten, except that beneath the comedy is something else. Theodora is fighting to survive; the burglaries are her closest call with drowning.

For all its ingenuities, its comedy and its occasional brittleness, “Midnight Sweets” is a cheerfully moving story. In her own way, Theodora is a gastronomical Mother Courage; except that at the end, entirely appropriately, she manages to defend not only life and children but a certain happiness as well.