An insurance salesman from Kentucky has become the first self-published author to sell one million e-books for the Kindle electronic reader.
John Locke used Amazon's Kindle Direct Publishing store to publish and sell his nine novels last year.
The part-time writer's crime thrillers and Westerns soon began racing out of the download store.
Locke, 60, has now become the eighth writer to join bestsellers Stieg Larsson and James Patterson in the Kindle Million Club.
His most popular character is former CIA assassin Donovan Creed, "a very tough man with a weakness for very easy women".
Lethal People, the first book in the series, was initially released in July 2009 as a small-run paperback by iUniverse, a company that enables writers to self-publish.
It was then re-released by Locke as an e-book in March 2010. Saving Rachel, a book in the Creed series, held the top spot in the Kindle Bestsellers list for three weeks and was joined by three other Locke e-books in the top 10.
Locke, who built his own insurance agency in Louisville, Kentucky, has just published his latest bestseller, a self-help guide titled How I Sold 1 Million eBooks in 5 Months.
He earns 50c from each $1.40 sale and will publish an eighth Creed book by the end of this month, with his third Western, Emmett & Gentry, following in July.
"It's a tough club to get into," the writer said of his entry into the million e-book selling pantheon, alongside True Blood creator Charlaine Harris and crime writer Michael Connelly.
The success of the Kindle is allowing word-of-mouth writers like Locke, who has no major publishing house or marketing campaign behind him, to outsell the literary world's biggest names.
Amazon announced in May that Kindle e-books are now out-selling paperback and print hardback titles combined.
Independent writers, offering budget-priced novels in popular genres like crime, can achieve huge success through strong word-of-mouth.
Established writers, used to prominent promotion in High Street book chains, don't get the same privilege in the Kindle store. Seven of the top 10 books in Amazon's digital bestsellers list are priced at $2 or less.
Neill Denny, editor-in-chief of the Bookseller, said: "It's a great achievement to sell one million copies but anyone who buys a novel purely on price is probably making a fundamental mistake. Locke will be bringing in new readers though, who might then pick up a Stieg Larsson."