Just a few years ago, self-publishing was synonymous with a rather less pleasant term: vanity publishing. The last resort of those unable to find a publisher, it entailed paying - rather than being paid - for a book to be produced and printed.
Such publishers still exist, and are popular with, for example, people wishing to publish their memoirs in an attractive book format; Amazon's CreateSpace is one of the more popular options. In recent years, though, the rise of e-publishing has revolutionised the market - and made writing just that bit less of a sure-fire route to penury.
EL James is the poster girl for this new wave of self-publishers. In 2011, her erotic novel Fifty Shades of Grey shot to the top of the best-seller lists; along with its two sequels, it's now sold over 90 million copies. Last August, Forbes magazine named James the highest-earning author in the world, raking in $95 million in a year.
Unfortunately, EL James is very much the exception. A recent survey by Digital Book World and Writer's Digest found that the median income for self-published authors is a rather less impressive $5,000, with nearly one in five reporting that they made no money from their books at all. Only 1.8 percent of self-publishers made over $100,000 a year.
But while most self-publishers receive a pretty poor return for the amount of time and effort they've put in, the rise of e-books has improved matters. They now account for a quarter of all book sales, and even out-sell hardbacks. And for many people with an unsold manuscript under the bed, it's a comparatively simple way of at least making *something* from all that hard work.
It's also useful for those whose books have been published in paper format but have now gone out of print, says science writer and thriller author Richard Milton, because it keeps the titles alive.
"I published a novel in 2000 called Dead Secret through a regular publishing house. Once it had gone out of print and the rights reverted to me, I put it on Kindle," he says. "It doesn't cost anything, the process is pretty simple and best of all the book will now stay there forever, instead of mouldering at the bottom of a trunk in the attic."
The biggest e-book publishing platform is undoubtedly Amazon's Kindle, which has around two-thirds of e-book sales. The Kindle Direct Publishing process is simple: authors simply upload their book, add sales copy and pricing information, and hit 'publish'. Books can be bought and read by anyone with an Amazon Kindle or the appropriate app for another device, such as iPad, Nook or PC.
The downside is that the company takes a royalty of either 30 or 65 percent of sales, depending on the book's price; however, self-published Kindle books have a good chance of doing well, with Amazon saying that they account for an impressive quarter of its top-selling 100 books.
For those wishing to cover the whole market, there are several other e-book platforms. Smashwords is the largest, with more than 180,000 titles on its list, and can convert a book into formats for all the major e-book stores. It charges a royalty of 15 percent.
Lulu, too, can convert a book into a number of formats; its charging structure is different, but amounts to a royalty of around ten percent on books sold through Apple's iBookstore (although Apple takes another 30 percent). It gets books into the Barnes & Noble online bookstore - which has 20 percent of the market in the US.
Two-thirds of self-publishers in the UK are women, research from Kingston University shows, and more than two-fifths have also been published in print. Three-quarters write fiction, with the rest split between poetry, biography, history, business support, reference, travel, personal memoir and self-help books.
"There has been a real tendency to think that self-publishing is a below-the-radar activity that has no effect on anyone. But it's increasingly having a big impact on what publishers commission and is changing the way the industry discovers what readers want," says researcher Dr Alison Baverstock.
"Soft porn aimed specifically at women and sometimes dubbed 'mummy porn' was unknown to much of the publishing industry before the Fifty Shades phenomenon. Increasingly, online material is selling to people with quite specific tastes that are not necessarily being catered for by traditional publishers, and the industry is having to sit up and take notice."