Investigating the murder behind The Great Gatsby

As well as Luhrmann's 3D extravaganza, in the last year alone The Great Gatsby has become a ballet, a graphic novel, an online computer game and there have been three stage versions, including Gatz, an eight-hour reading of the text.

Meanwhile, Fitzgerald's wife Zelda is having her moment, with no fewer than four novels about her, including New York Times bestseller, Z: A Novel Of Zelda Fitzgerald, by Therese Ann Fowler. Recently, BBC Radio 4 broadcast a dramatised version of Fitzgerald's final, unfinished novel, The Last Tycoon, adapted and directed by Greenock-born Bill Bryden.

And then there's Churchwell's dazzling book. Careless People is a thrilling detective story and a "biography" of Fitzgerald's strange, seductive, slim novel – "48,885 words, if you take out the epigraph and chapter headings," notes the Professor of American Literature and Public Understanding of the Humanities at the University of East Anglia (UEA), who is also a respected critic and popular broadcaster, following her many appearances on "the almost late and almost lamented" BBC Two Review Show, to which she brought a creamy blonde glamour and laser-sharp intellect.

London-based Churchwell has worked on Careless People, which tells "a remarkable tale of murder, adultery, class resentment, mistaken identity and the invention of comic pasts" for four-and-a-half years. Her publishers announced they had acquired her book just as Luhrmann's movie – the fourth attempt to film a novel that is unfilmable to those of us who are in its thrall – got the green light.

Almost immediately, Churchwell received a call from one of the Australian director's assistants, saying they'd like to read her book. "I laughed and said, 'So would I!' From that point on it's been a bit of a race," she admits, sitting in the lobby of a London hotel. "I'm a scholar. While Luhrmann has taken on the myth of the book, I am saying, 'Here's what the world really looked like in 1922, the year in which the book is set.' I wanted to explore the realities, the histories of that world; it was such a strange, sinister time, much darker than we tend to think. I tried to find out what was in the air. I made many discoveries so this remarkable novel still has some surprises left. I also wanted to write a book that has its own pleasures, that's fun to read." But with intellectual heft? "Oh sure! I worked so hard at the writing. I wanted to do justice to Fitzgerald as much as I could and to do justice to the novel that he called 'a wonder'."

The first thing I tell her is that I rarely leave home without a copy of The Great Gatsby about my person; I have read it countless times. I thought I knew this beautiful book by heart. After reading Churchwell's "histoire trouvé", I read it again as if for the first time. Her book is a revelation.

She thanks me then tells how she met a woman in New Zealand recently who had an early proof of the book, which like the novel is made up of nine chapters, each beginning with Fitzgerald's corresponding note from the enigmatic outline he scrawled on the back of Andre Malraux's Man's Hope. "She had read a chapter of my book, then the relevant chapter in the novel. I'd never thought of doing that. Of course I always assumed my reader would be smart – anybody who likes The Great Gatsby is!

"I am very suspicious of anyone who doesn't love Fitzgerald. His books are so much fun – he was a very funny man, with such a strong sense of humour, but critics tend to strip all the joy out of him. My book began as a biography of The Great Gatsby, which I'd begun reading around in 2009, because I've always known I'd write about Fitzgerald one day. I really wanted to stress what a pleasurable read The Great Gatsby is, what a peculiar little book it is, too, but peculiar in the best possible way, a work of genius, a hymn to language, a prophetic glimpse into the world to come. Yes, Fitzgerald was a great writer but he was also a thinker."

Then she stumbled across literary gold: the notorious Hall-Mills murder in New Jersey, a mystery which she weaves throughout the book and which took place in the autumn the Fitzgeralds returned to New York and began the riotous partying that inspired The Great Gatsby. She believes the scandalous case has many parallels with the novel and has pored over hundreds of newspaper files to investigate it. "I thought I knew the genesis of The Great Gatsby well; it turns out I didn't. But I really want to keep it under wraps for readers."

One of her models for Careless People was Kate Summerscale's The Suspicions Of Mr Whicher. "In reverse," she explains. "Where that book reconstructs a crime and then tries to solve it, bringing in literature, I start with literature and bring in the crime and try to solve it. So it was a challenge to write narratively and forensically and yet reconstruct the mystery to give the reader the pleasure of a novelistic read but never cheat on the facts. It was hard work!"

Churchwell's previous books include The Many Lives Of Marilyn Monroe. "There is a commonality for me, intellectually, between her and Fitzgerald. They are about celebrity and glamour, but also our distrust of glamour and of popularity. Why can't you be good and popular? The Great Gatsby is a perfect example of that – it's magnificent and popular."

Virginia-born but raised near Chicago where she was educated before graduating from Vassar then Princeton, she always wanted to write. "But it took a long time. The assumption then was you'd write fiction – it's one of the things I identify with Zelda on. I'm not particularly good at plot, neither was she as anyone who has read her novel, Save Me The Waltz, recognises. As I got older, though, if it's not an obnoxious thing to say, I discovered I have a pretty good analytical brain and a pretty good critical brain; I'm a logical thinker. Academia suits me and I love teaching. It's a privilege to share my passion.

"I'm an economic migrant. I was ready for an adventure when the job came up at UEA, where they then had WG Sebald, Malcolm Bradbury and Lorna Sage. Yeah! What I didn't know was that the adventure changes you, you put down roots, you make a life, you build a career." (She is married to an English businessman, whose identity she can't divulge for legitimate off-the-record reasons.)

Her parents met at law school, although they eventually divorced. Her mother, Judith, was one of the first women to be accepted by the school. "It was the early 1960s and she was bullied out – a very formative thing for me to learn," reveals Churchwell, who is "somewhere between 35 and 45". She first read The Great Gatsby in high school. She was 15. "I loved it but I remember feeling frustrated because I didn't understand why I loved it in this mysterious way. That became a driving force for me.

"My students will tell you I always use the example of it in class – my job is to make you understand why this is a great book, his greatest. I always knew I'd delve into the heart of it one day. Now I know Fitzgerald will be part of my intellectual and creative life forever."

Indeed, she's thinking about another two books on him. She quotes a letter he wrote before he died to his daughter, Scottie, about Keats's Ode On A Grecian Urn and what it means to appreciate beauty. He wrote: "I suppose I have read it a hundred times. About the tenth time I began to know what it was about, and caught the chime in it and the exquisite inner mechanics." That, she says, is what she desperately wanted to do, to explore the "exquisite inner mechanics" of The Great Gatsby. She has succeeded, gloriously catching the chime in it.

Careless People: Murder, Mayhem And The Invention Of The Great Gatsby is published on June 6 by Virago, priced £16.99