Five years ago, when HarperCollins approached me about writing a biography of John Updike, I would have classified myself as a moderate fan, thrilled by his supple, precise prose and respectful of his wide-ranging talent and effortless industry: every year a new Updike book! I admired many of his novels and most of his criticism; though aware of his poetry, I hadn't read very much of it. It was apparent to me even then that Updike had earned himself an exalted place in the pantheon of 20th-century short story writers.
Now, after a thorough immersion in all things Updike, my admiration has spread and deepened. I've come to cherish many of his poems, and the large majority of his 23 novels. After countless hours in the archives, I've discovered Updike the helplessly prolific letter-writer, scattering literary jewels throughout a vast correspondence. But Updike's stories – there are 186 of them in the two-volume Library of America edition – remain for me the chief glory of his collected works. His stated aim in his short fiction was "to give the mundane its beautiful due", and it's an aim he achieved beautifully.
An Updike alter ego, John Nordholm, looks back in tender reminiscence to a time when he was a second-year student at university. He has been home for Christmas at his parents' farm, and is leaving again. He's eager to put his childhood behind him and at the same time desperate to preserve the past intact, to protect and cherish it. The tension between these two impulses supplies the emotional power here, as it does in many of the stories Updike wrote about Olinger, a lightly fictionalised version of his Pennsylvania hometown, Shillington. While writing this story, Updike later explained, he had "a sensation of breaking through, as if through a thin sheet of restraining glass, to material, to truth, previously locked up".
A devastating story about the break-up of the marriage of Richard and Joan Maple, stand-ins for Updike and his first wife. It features a tragicomic last supper at which Richard, an unfaithful husband and flawed father, is supposed to inform his children that he and their mother are splitting up. At the end of the story, his eldest son asks him "why?" – which prompts an indelible final paragraph: "Why. It was a whistle of wind in a crack, a knife thrust, a window thrown open on emptiness … Richard had forgotten why." Minutely autobiographical and gorgeously shaped, Separating is perhaps the world's best (and worst) argument for writing about what you know.
Updike's most widely anthologised story, about a boy working at the checkout counter in a supermarket and the three young pretty girls who walk in wearing nothing but bathing suits. As Updike's first wife pointed out, the teenage narrator's voice ("In walks these three girls … ") is very Salinger – but the dazzlingly vivid detail and the quixotic romanticism are pure Updike.
A sequel of sorts to his brilliant early novel Of the Farm (1965), as well as a memorial to his widowed mother who died in 1989 and is here is resurrected with unsentimental candour and evident affection. Updike filled the story with incidents snatched directly from her last six months, quoting her verbatim and giving the precise circumstances of her death by heart attack. An attempt to immortalise the most important person in his life, it was also, for him, a kind of therapy.
As the story's comically long-winded title suggests, Updike here stitches together disparate elements, a daring collage construction. Among the many marvels, this striking description of how fiction writers condense and transform experience: "We walk through volumes of the unexpressed and like snails leave behind a faint thread excreted out of ourselves."
The first (and sweetest) of 20 stories featuring Henry Bech, another – this time rather unlikely – Updike alter ego. A New York Jewish writer, Bech is in some ways everything Updike was not: an anguished urban bachelor beset by writer's block. But thanks to Bech, Updike was able to record in fiction an important part of his experience: the life of a professional author. In this story, Bech is travelling behind the Iron Curtain, as an ambassador of the arts, sponsored by the US government. (Updike did the same, the same year.)
Returning to eastern Europe decades later, our hero visits Kafka's grave, meets a handful of dissidents, broods about the Holocaust, and suffers an attack of anxiety that is at once existential and postmodern: "More fervently than he was a Jew, Bech was a writer, a literary man, and in this dimension, too, he felt a cause for unease. He was a creature of the third person, a character. A character suffers from the fear that he will become boring to the author, who will simply let him drop."
The problems in this very short and ostentatiously clever story are presented as questions on a maths test: "During the night, A, though sleeping with B, dreams of C … Problem: Which has he more profoundly betrayed, B or C? The story, from a collection of the same title, is emblematic of the brief moment of guilty limbo between Updike's first and second marriages, a period during which divorce and its discontents replaced adultery as his simplex theme.
A bittersweet record of the court hearing that put an end to the Maples' marriage. The 17th of 18 stories chronicling more than two decades of the couple's quarrels and reconciliations, it's a barely fictionalised yet artful retelling of Updike's own experience in the divorce court. The concluding kiss is priceless.
Like The Happiest I've Been, this is a story about a university student who's come home for the holiday and is now leaving again. Updike was 26 when he wrote the first story, 73 when he wrote the second. There are fewer bravura moments in My Father's Tears, less writerly zeal, and yet it achieves a quiet, sober intensity. The reason for the father's tears? "I was going somewhere," the son tells us, "and he was seeing me go." Updike's talent had mellowed and deepened; it certainly hadn't diminished.
• Updike by Adam Begley is published by Harper, priced £25. Buy it from the Guardian bookshop