LORD help us all when aunts start writing books. On the other hand, you would read a book by Shakespeare's aunt wouldn't you? Bound to be something in it. In Truman Capote--billed on its jacket as "the story of his bizarre and exotic boyhood by an aunt who helped raise him"--there is, just for instance, the following story about Capote's mother, Lillie Mae:

"Whenever she came to a puffball, she kicked it impatiently. We watched the small clouds of mustard-green smoke that erupted each time she stepped on one.

"Suddenly Lillie Mae whirled around, her skirt lifting up and exposing her slim brown thighs and calves. Her feet were small and highly arched. She was completely confident.

" 'I swear, Clay, wouldn't this be a perfect place to take our pleasure?' Lillie Mae said saucily. 'Why, every move we'd make would explode a puffball!'

". . . They stopped and then lay down in the underbrush among the bloodroot and puffballs."

Clay is Lillie Mae's Monroeville, Alabama beau for the afternoon, Truman's father being in New Orleans. The narrator is Marie Rudisill, the aforementioned aunt, who accompanied her sister Lillie Mae on trysts for appearances' sake. She has written this book with James C. Simmons, a scholar of the Southern Renaissance. Mustard-green smoke erupts on every page.

Here are some of the other things Mrs. Rudisill confides:

* Truman's mother didn't love him. He once overheard her telling the cook, "I just can't stand the sight of my son. . . . He's just like his father sometimes--Little Miss Mouse Fart." Most of the time she left him in the care of his aunt and his four grownup cousins, one of them a lifelong bachelor and the other three spinsters, in their house in Monroeville. Sometimes Lillie Mae stayed there too, but when she did Truman drooped.

* Truman's mother didn't love Truman's father, either. His name was Arch Persons.

* Truman's father gave scant evidence of loving Truman. He was usually away doing things like selling tickets to the burial and resurrection of a down-and-out Egyptian named Hadjah, who could control his breathing, but who was dead when last dug up.

Truman loved his dog, which although it was male he insisted on calling Queenie.

Truman's mother was some number. When she moved to New York, she tried to seduce a Catholic priest during communion: "When she knelt at the railing, she strained every muscle in her body, so that her breasts looked as though they were ready to pop right out of her blouse." The man she always preferred, but would not marry because he was a Creek Indian, was Tecumseh Waterford. Mrs. Rudisill would often accompany Lillie Mae to meet this romantic figure in the woods, where the lovers would "talk and act as though I were not even there." She was, though.

* Truman's stepfather, whom Lillie Mae left in New York, was a "chubby little Cuban gentleman" named Joe Capote, who was on the way to Sing Sing for embezzlement when Truman's mother took a fatal overdose of sleeping pills: "The final blow came the day that Joe pawned her full-length mink coat."

* Truman's mother continually berated him for effeminacy, but just before her death Truman felt that the two of them were approaching an understanding. By then he was a literary light. "My contacts with Grace Kelly and Princess Margaret," he told his aunt, "were so important to her."

* The strongest figure in Truman's childhood was his middle-age cousin Jenny Faulk, a lady's clothing entrepreneur who ran the household in Monroeville with an iron will, who caused a fence of animal bones to be erected around the garden, who horsewhipped her sister Callie's fianc,e out of town, and who had discreet affairs. "In the front yard hidden beneath the rosebushes was a small tombstone that read simply, 'ONE DAY OLD.' Jenny would never answer our questions about it."

* The person who showed young Truman the most affection was his childlike grownup cousin Sook. She joined him enthusiastically in fantasizing, kite-making and dressing up in women's finery, but she wouldn't let him ride his bike except right around the house. "Youse gonna make a man-chile into a split-tail chile if yo ain't careful," complained the cook. (For the most part this book evinces a good ear, but it is wrong in using "yo" to mean "you." "Yo" is short for "yore.")

* Those readers who know of Sook through Capote's story "A Christmas Memory," which has a character lovingly based on her, will be disturbed to learn that her bedroom stank because she wouldn't let any fresh air into it and that she hated blacks and Yankees. She informed Truman with relish that her father once punished a ham-stealing field hand by nailing him up in a rain barrel with long nails driven into its sides and rolling him downhill.

* Truman's elderly cousin Bud was fond of Truman and told him wholesome stories. Bud was in several ways a Negrophile, and a nice man. But he never worked or married. Except presumably with regard to blacks and Yankees, "Sook's influence," says Mrs. Rudisill, "eventually proved the stronger."

* Monroeville also offered Truman great soul food, spooky neighbors, neat places to sit alone and think, and family retainers who did voodoo and said things like "Don't y'all spit in de fire. It will dry up yore lungs." There were also friends his own age, notably including Nelle Harper Lee, who later wrote To Kill a Mockingbird. Nelle and Truman would get out a typewriter and a dictionary and play writer for hours. Nelle could knock Truman flat and jump up and down on him like a rooster, but Truman's imagination, energy and flair for tall tales made him Tom Sawyerishly dominant among the kids.

* When Truman came back to Monroeville as a famous writer, a prominent local banker invited him to lunch. Truman told him to move his bowels up a stick. "Simply because he was a nobody," Truman explained to his aunt, "and he only wanted to be seen with a somebody."

Few aunts, thank God, broadcast family anecdotes as vividly as Mrs. Rudisill does, or as shamelessly. But she is an aunt, with an aunt's perspective, and to her Truman remains not only a nephew, but one who has refused to take her phone calls for 15 years. The most recent image of him she provides is at the age of 30, after his mother's death, crying "as a small boy cries, pressing his mouth hard against the white knuckles of his fist."

We should remind ourselves that a person's development may be somewhat more mysterious and advanced than it seems to his aunt, and that Capote is a person who--however unseemly his relish in seeing himself as a "somebody" may be and however childishly he may cry --does have mature achievements to his credit. He has also published some misty stories of youth, and some nasty stories from other people's lives, that this book interestingly complements.

Capote must have been an appealing, if formidable, little kid. Cousin Bud predicted he would be famous. (I'm glad to have read about Cousin Bud. I never knew anybody named Bud I didn't like.) Mrs. Rudisill recalls walking into town with Truman and Nelle on hot sidewalks. "Occasionally Truman would step over into the dirt street and dance a few steps of the Charleston to cool the bottoms of his feet in the warm dust."

Damn parents who don't love their children.