The world of publishing can be extremely competitive, with somewhere between 600,000 and 1,000,000 books published every year in the US alone. It’s estimated that around half of those are self-published and sell fewer than 250 copies. But a successful self-publish can make a lot of money. Here are some of the big names that have made it on their own.

Self-publishing has been around for decades. Professional writers and amateurs have often resorted to putting their own books out, either because conventional publishers weren't interested or as a way to retain editorial control. But when e-readers, such as Amazon's Kindle, exploded in popularity in the mid-2000s, self-publishing became big business.

There are many online platforms to self-publish, and authors find the speediness and ease of use appealing, as books can be available for download in as little as 24 hours from when they are uploaded. The royalties are also appealing, with self-publishers getting up to 70% of the profits of their labor, compared to just 10% on average in conventional publishing. Authors do have to do their own marketing legwork though, and that can be what propels an e-book to the top of the charts. Let's take a look at some of the biggest success stories.

The Wealthy Barber might be one of Canada’s best-selling books of all time, but it started out being sold from author David Chilton’s basement before becoming a popular series. Chilton had been working as a small time stockbroker outside Ontario when he decided to put pen to paper and share his personal finance insights with the world in the form of The Wealthy Barber, a parable about a stingy small-town guy who saves and invests his way to fortune.

The first book in the series, self-published by Chilton in 1989, sold over two million copies in Canada. He released The Wealthy Barber Returns in 2011. Chilton is such a firm believer in self-publishing that he spent years consulting with other Canadian self-publishers to help them succeed. He has since made the transition from author to TV star in Canada’s version of TV series Dragon’s Den and is reportedly worth $15.5 million (£12 million), largely from The Wealthy Barber franchise.

Paul Pilkington, a university lecturer from the north-west of England, decided to write suspense thrillers after reading the popular Harlan Coben books 14 years ago. When he received a Kindle as a Christmas present, he chose to self-publish his own series based around the exploits of Emma Holden, an ordinary woman thrust into an extraordinary situation when her fiance goes missing in London.

Pilkington has sold over 3,000,000 copies of his Emma Holden books, and has consistently featured in best-selling e-book charts. His success in self-publishing has led to a three-book deal with UK publishing giants Hodder and Stoughton. Despite finding e-Book stardom, Pilkington has not left the day job, and works on his novels for an hour a day, either before or after he leaves the university where he works.

Arguably the most well-known self-publisher ever, Erika Mitchell had never written a word before 2009 when she joined a fan-fiction website for admirers of the Twilight saga. The then-studio manager from High Wycombe, England, became enthralled with the possibilities writing offered her, and decided to take her fan-fiction one step further. She self-published 50 Shades of Grey under the nom-de-plume E. L. James, and it was an instant online success.

Two more books followed in rapid succession. Before long, the 50 Shades trilogy was picked up by Vintage Books (a conventional publisher). By 2013 Mitchell was a multi-millionaire. Her three-book series was universally panned by critics, but made her $95 million (£74 million), $5 million (£3.9 million) of which came from the three-movie option rights bought by a Hollywood studio. Drawing on her background in film and TV, James is credited as a producer on the film adaptions of her books.

Alabama native James Redfield spent much of his 20s studying Eastern Philosophies like Taoism and Zen, before working as a therapist for abused teenagers for over 15 years. He left his job in 1989 to focus entirely on writing, as he wanted to bring messages about mysticism, futurism and ecology to the general public. He self-published his first book, The Celestine Prophecy, in 1993.

The Celestine Prophecy follows a narrator as he tries to reveal a series of nine spiritual insights he found in an ancient Peruvian manuscript. Redfield initially sold the book from the boot of his car. He had sold over 100,000 copies before Warner Books picked it up. It’s sold over two million copies worldwide since. Today Redfield runs the Celestine Vision project, which endeavors to spread his spiritual message.

Born in a small town in Ontario, Canada, K.A. Tucker published her first book at the age of six with the help of her elementary school librarian and a box of crayons. As an adult Tucker has been self-publishing novels since early 2011. Her Causal Enchantment young-adult series has a devoted following online, after she published it using Amazon’s self-publishing e-book service for Kindle.

When she published an adult contemporary novel, Ten Tiny Breaths, big publishers started taking notice because of her established fanbase. Ten Tiny Breaths follows a young woman trying to rebuild her life after a drink-driving accident, and led to a five-book deal with Simon & Schuster.

Rachel Abbott had a long and successful career in data analysis and interactive media in Manchester, England, before she started writing. She had no plans to self-publish when she wrote Only The Innocent in 2011, but her family and friends who read it loved it so much they persuaded her to change her mind after it was rejected by conventional publishers. In just three months the debut novel had soared to number 1 on Amazon UK’s Kindle shop after a concerted marketing effort by Abbott.

Bolstered by her initial success, Rachel has now written six novels, all self-published, and sold over two million copies of her books. “The pros of self-publishing are that as the author you have complete control over your books and how they are priced, marketed, what the covers look like, etc,” she told writersincharge.com. “You also receive a much higher proportion of the income.”

When Tracy Bloom moved to Connecticut, US from Derby in England, with her husband and small baby, she left behind a successful career in roller coaster and theme park marketing. Without work in the US, Bloom decided to take her chances with self-publishing. Her debut novel No-One Ever Has Sex On A Tuesday was an overnight success and became an e-book number 1 bestseller in the UK within nine weeks.

Unlike other authors, who find success by self-publishing leads them to a conventional publishing deal, Tracy Bloom has continued to publish her novels herself. She has five other novels out, all available exclusively as e-books. She now describes herself as an "authorpreneur", and has never gone back to conventional work, focusing instead entirely on her writing and marketing her e-books.

H. M. (Holly) Ward is arguably one of the most successful self-publishers of all time. She always knew her style of female new-adult literature would struggle to find a home in the mainstream publishing world, so she committed to self-publishing. Ward has sold close to 13 million copies of her adult novels. Unusually for a self-publisher, 21 of Ward’s titles have appeared on the New York Times Best Seller list.

Her first novel, Damaged: The Ferro Family, appeared in the Top 100 Kindle Titles list for over 100 days. It became the first in a series focusing on the Ferros’ exploits. All of her novels are self-published though Ward's own press and she's a vocal proponent of the industry − she now leads workshops for aspiring self-publishers. So popular are the Ferros that there's an active fan-led petition to turn Ward's series into a major motion picture.

Michael J Sullivan is widely considered one of the most successful self-published sci-fi authors of all time. He has been a professional writer since 1979, but after 13 book flops he quit the industry in 1994, tired of the rejection from mainstream publishers. By 2002 he couldn't stay away from the computer any longer and composed a a fantasy novel for his daughter. He eventually decided to market the Riyria Revelations, but his publisher went bankrupt after the first book came out.

Despite the setback, Sullivan bought back the rights to his book, and set up his own publishing company in 2008 in order to release The Crown Conspiracy. Sullivan’s fantasy epic collection was so successful that he sold 90,000 copies before signing with publishers Orbit, a division of Hachette. The series of six books was released under the Orbit banner and has since been translated into 14 languages.

A native of Minnesota, Amanda Hocking wrote her first 17 novels while still employed as a group homeworker caring for severely disabled people. She'd write after work, fueled by energy drinks. After countless rejection letters, she'd never thought she'd see her name in print. In 2010, Hocking needed a little extra cash for a trip so decided to self-publishing her vampire romance series My Blood Approves as e-books; within a year she had sold over two million copies of the nine-book series.

It was reported that Hocking netted close to $2 million (£1.6 million) from her self-published books in that first year. In 2011 she was selling an average of 9,000 e-book copies a day. She has since signed with conventional publisher St Martin’s Press, a division of Macmillan, which reportedly paid her another $2 million (£1.6 million) for a new paranormal book series, Watersong.