“There never was a good biography of a good novelist,” F Scott Fitzgerald wrote in his notebooks. “There couldn’t be. He is too many people, if he’s any good.”

Fitzgerald was indeed many people and was never entirely able to decide which one he wished to be. Born in 1896 into a middle-class Catholic family in St Paul, Minnesota, he was, like his most celebrated protagonist, the deluded romantic dreamer and bootlegger Jay Gatsby, beguiled by the ease and confidence of the old moneyed elite from whom he always felt excluded. He described his family ancestry as “straight 1850 potato-famine Irish”.

An early hero of Fitzgerald’s was the gentleman-sportsman Hobey Baker. He is, surprisingly, not mentioned by the academic and critic Sarah Churchwell in her new book about Fitzgerald, Careless People. An ice hockey and American football champion, Baker served as a fighter pilot during the first world war but was killed in an aviation accident in December 1918, aged 26. For Fitzgerald, he represented an ideal of masculinity: courageous, daring, charming, privileged. Everything that he aspired to be.

Fitzgerald was both a stubborn moralist who, in his fiction, simultaneously satirised and venerated Jazz Age excesses, and a hedonist whose drunken stupidities are tirelessly catalogued by Churchwell, as they have been by previous biographers.

A literary modernist who was as much influenced by Conrad as he was by Keats, Fitzgerald also wrote lucrative commercial magazine fiction, and this led to feelings of self-disgust. “I really worked hard as hell last winter – but it was all trash and it nearly broke my heart,” he said in a letter to Edmund Wilson in 1924.

John Updike wrote that Fitzgerald is an “author one should read when young”. That seems just right. I discovered him when I studied his fourth novel, Tender is the Night, for A-level. I’d spent my early teens reading nothing more demanding than comics and the sports pages of newspapers, and yet the combination in Fitzgerald of romance and nostalgia as well as his exquisite poetic prose enthralled me. I began reading everything I could by and about him.

One understands why Fitzgerald continues to attract the biographer’s gaze. His life was tremendously glamorous yet also ultimately a failure, at least on his own terms: his best novel, The Great Gatsby, was published before he was 30, and the last years of his life before his death at the age of 44 were spent hacking around Hollywood as a scriptwriter (he worked on Gone with the Wind, among other films).

By then Fitzgerald, who was an alcoholic and separated from his mentally ill wife Zelda, was receiving only $200 for short fiction; in the early 1920s he was paid as much as $4,000 a story. The 1920s were his time, when he and the beautiful and careless Zelda were the talk of Manhattan.

Churchwell says her book is “an histoire trouvé about what was in the air as Fitzgerald wrote The Great Gatsby”. She concentrates largely on the year 1922, when the Fitzgeralds were renting a place on Long Island. Careless People is a collage of breezily written texts combining conventional biography and literary criticism with reportage and capsule essays on style, fashion and the movies.

Interweaved throughout is the account of the double murder of a couple from New Jersey, an Episcopalian minister named Edward Hall and his lover Eleanor Mills. “The scandalous murders of Hall and Mills were impossible to miss. They would be front-page news across the country for the rest of 1922”, Churchwell writes, but neglects properly to explain why the story of this unsolved murder is especially relevant to Fitzgerald or his great novel and why she should dedicate so many pages to chronicling the investigation into it.

It’s worth recalling that Gatsby, perhaps the most perfect short novel in English, comes in at 172 pages in a standard Penguin paperback edition. Careless People is nearly 450 pages long and would have benefited from being half that.

I must have read Gatsby at least a dozen times and still cannot resist returning to it. Few writers use adjectives and adverbs more seductively than Fitzgerald. He writes for instance of the “fluctuating, feverish warmth” of Daisy’s voice; of the day the “world and his mistress returned to Gatsby’s house and twinkled hilariously on his lawn”. Nearly every paragraph offers something perfectly pitched: something precise, radiant, alive.

Fitzgerald, learning from Keats – he especially admired “Ode on a Grecian Urn”, which tells us that “Heard melodies are sweet, but those unheard/ Are sweeter” – locates happiness in the search for sensation rather than in its realisation, in the dream of desire, not in its fulfilment. He was unashamedly romantic and could be as sentimental as any tormented adolescent lover.

Updike mocked what he called Fitzgerald’s “eternal undergraduate effluvium”. Hemingway once said this to his old rival: “You put so much damned value on youth it seemed to me that you confused growing up with growing old.” Yet HL Mencken articulated something essential when he said that Fitzgerald succeeded in capturing the “inexplicable tragedy of being alive”.

By the time of his death in 1940, Fitzgerald was no longer celebrated, if he was read much at all. He died pretty much defeated and disillusioned, exhausted by alcoholism and by worries about money and Zelda’s mental health. Yet years earlier he had written to his editor, Maxwell Perkins, expressing belief in his talent. “I feel I have an enormous power in me now,” he said while revising Gatsby. Which reader today does not still feel that power?