A cache of unpublished works by famed writer Dashiell Hammett, often seen as the father of hardboiled detective fiction, has been found and is set to be unveiled in America.

Hammett, whose best-known work The Maltese Falcon was made into a film starring Humphrey Bogart, died in 1961. Now 15 unpublished short stories are to hit the bookshelves after being unearthed by a magazine editor, Andrew Gulli, among the literary archives of the Harry Ransom Centre at the University of Texas in Austin.

Gulli will now publish one of the stories in his crime fiction magazine, The Strand, later this month. He hopes to eventually help publish them all as a collection in a new book.

"There are some very, very good pieces of fiction here. Some of them are classic Hammett and fit in with the style we know and others are very different and go off to places that were a different direction for him," the editor said. The Hammett discovery is just the latest in a series of coups by Gulli's magazine. In recent years The Strand has also printed previously unseen works by Graham Greene, Mark Twain and Agatha Christie.

The Hammett story that will feature in The Strand is a piece of straight detective fiction, but it is written in the style the writer pioneered and perfected. Called So I Shot Him, it tells the tale of an afternoon by a lake that goes horribly wrong. It opens bluntly with the title sentence and then goes on in a rat-a-tat style familiar to Hammett's legion of fans. The dialogue is crisp and deadpan and the characters memorable, said Gulli. "After reading it, you will be debating it and wondering exactly what it means and then you'll want to go back and read it again."

The news of the undiscovered works has some crime fiction experts delighted at the prospect of studying fresh material from a man many consider to be a popular genius. Besides The Maltese Falcon, whose hero was the crafty hard-bitten gumshoe Sam Spade, Hammett also wrote The Thin Man and Red Harvest – the latter was once named on a list of Time's 100 best novels in the English language.

"We can never have enough Hammett. This news is very exciting. There is a prospect of being able to research and understand stories that have never been published before," said Tom Nolan, an expert on detective fiction and a literary critic for the Wall Street Journal.

Hammett, along with other writers of the 1920s, 30s and 40s such as Raymond Chandler, defined a new fictional world with their gritty portrayals of urban America. They eschewed straightforward heroes and villains for chancers and grifters who worked both sides of the law. These low-life characters and anti-heroes were a ground-breaking development for most mass fiction and still influence crime novels today.

"The hardboiled approach was to be an agent of reality. It developed as a way of exploring American cities and this new urban environment that people were living in. Hammett is as relevant as any of the better known American writers of the day like Ernest Hemingway or John O'Hara," Nolan said.

Hammett lived as colourful a life as any other writer or indeed any of his characters. His inspiration for the worlds he created came from his time spent as a detective for the Pinkerton National Detective Agency from 1915 to 1922.

However, he was also a political activist and a fervent supporter of leftwing causes and the labour movement. By 1934 he stopped writing full novels and devoted most of his time to political causes, including joining the American Communist party. He was eventually blacklisted in the 1950s by Congress's notorious house un-American activities committee. A fondness for hard drink also took its toll and he died a virtual recluse in a New York city hospital.

Now the discovery of new work adds an unexpected final chapter to Hammett's literary life. Gulli said he had no idea how or why the works were in the Texas archive or when they were written as none are dated. "They could have been written anytime in the 1920s or 1930s or 1940s," he said.

But, in a typical Hammett plot device, they now provide an unexpected twist at the end of a narrative. As many of the works, including So I Shot Him, deviate from the traditional settings of his previous detective fiction, they show that Hammett was a talented writer beyond the literary niche he was best known for. Hammett, Gulli says, should now be seen in a very different light. "He was drifting into something else. We have discovered that he was a far more versatile writer than he ever gets credit for," Gulli said.

Extract: So I Shot Him, by Dashiell Hammett

Rainey screwed himself around in his chair to see us better, or to let us see him better.

I was sitting next to him, a little to the rear. Above the porch rail his profile stood out sharp against the twilight gray of the lake, though there was nothing sharp about the profile itself. It had been smoothly rounded by thirty-five or more years of comfortable living.

"I wouldn't have a dog that was cat-shy," he wound up. "What good is a dog, or a man, that's afraid of things?"

Metcalf, the engineer, agreed with his employer. I had never seen him do anything else in the three days I had known them.

"Quite right," he said. "Useless."

Rainey twisted his face farther around to look at me. His blue eyes – large and clear – had the confident glow they always wore when he talked. You only had to have him look at you once like that to understand why he was a successful promoter.