Nora Roberts is one of the world’s most popular authors. She’s written more than 200 novels, tackled topics from romance to murder and sold more than 500m books around the world. And now she’s really, really angry.

Roberts is one of dozens of authors who discovered last month that their work had been allegedly plagiarised by a Brazilian romance novelist called Cristiane Serruya. “Leisurely, he began to loosen her hair, working his fingers through it until it pooled over her shoulders. ‘I’ve wanted to do that since the first time I saw you. It’s hair to get lost in,’” runs Roberts’ novel Untamed. Serruya’s Forevermore has it that: “Leisurely, he began to loosen her hair, working his fingers through it until it pooled over her shoulders and cascaded down over her back. ‘I’ve wanted to do that since the first time I saw you.’”

Serruya’s alleged plagiarism was first exposed by US author Courtney Milan, who found passages from her book The Duchess War in Serruya’s novel Royal Love. After Milan went public – and after dozens of other examples of plagiarism were highlighted by authors and readers – Serruya pulled her books from sale, blaming the overlaps on a ghostwriter she said she’d hired from freelance marketplace Fiverr.

A former law professor, Milan was a dreadful choice to lift from – as was Roberts, who has never been sanguine about plagiarism, taking her fellow novelist and former friend Janet Dailey to court in 1997. But Serruya is just one example of the dark side of the stack-em-high, sell-em-cheap, flood-the-market culture which has come to dominate self-publishing – particularly in the lucrative romance genre and on Kindle Unlimited, an Amazon service which gives readers access to more than 1m books for £7.99 a month, many of which are self-published and unvetted for plagiarism.

This culture, this ugly underbelly of legitimate self-publishing is all about content. More, more, more, fast, fast, fast Nora Roberts

“I’m getting one hell of an education on the sick, greedy, opportunistic culture that games Amazon’s absurdly weak system. And everything I learn enrages me,” Roberts wrote on her blog last month. She pointed to what the industry calls “black hat teams”: anonymous authors who hire ghostwriters for a pittance, to churn out cheap novels en masse which are published under a pseudonym to “smother out competition” – and, in some cases, copying lines or entire scenes to get the job done. A regular author could never keep up.

For romance readers, Kindle Unlimited (KU) has been a godsend. These readers can race through at least a book a day, gulping down stories about unexpected pregnancies, arrogant millionaires and bad boys in need of taming. KU means they can read to their hearts’ content, while the writers can make a lot of money. Authors who self-publish through Amazon’s Kindle Direct Publishing (KDP) Select programme have their books automatically enrolled in KU. Every time a reader opens a KU book, the author is paid from a communal pot of money – one which less scrupulous writers have looked to game from the start.

When KU was launched five years ago, authors were paid by Amazon from a monthly pot each time more than 10% of their book was read. Scammers descended, publishing books running to just a handful of pages, filled with worthless text but earning their “authors” money each time they were clicked on.

So Amazon changed the system. Now, authors are paid depending on how many pages of their books are read. The more pages read, the more money made. And there is, potentially, a lot of money to be made: the monthly pot in February was $23.5m (£17.7m).

But where there is money to be made, there are scams to be run. Last year, several KU writers noticed a rise in what is known as “book-stuffing” – authors publishing extraordinarily long books, filled with vast amounts of questionable additional content, along with an incentive to head to the last page.

When authors are paid around $0.005 per page, a reader making it to the end of a 3,000-page book would make the author $15. Knowing this, and pouring money into Facebook ads, drowning readers in marketing emails, offers and giveaways, the top scammers are estimated to be making up to $100,000 a month.

Authors fight back

Rise of the scammers is ‘exponential’ … campaigning author David Gaughran. Photograph: Scott King

Author David Gaughran has waged an often lonely campaign against ebook scammers for years, and he describes their rise since KU was launched in 2011 as “exponential”. Last summer, he helped to highlight the case of Chance Carter, a romance writer who described himself as “a bad boy who writes about bad boys”. Carter’s novel Mr Diamond, about a Russian man who is being forced into an arranged marriage by his father, but who falls for the woman behind the Tiffany’s counter selling the engagement ring (she “makes my heart pound, my pulse race, and my … how you say? ... weapon get hard as Russian steel”), was just a drop in the lake of bad-boy romances already published by Carter (Bad Boy Daddy, Most Eligible Baby Daddy, and the inexplicably named Wife Me Bad Boy).

Aside from all the questionable prose, Carter was offering what he called “bonus content”, which amounted to six extra novels stuffed into the back of Mr Diamond. Despite authors being banned from incentivising reviews, Carter also included a competition: if readers reviewed the mammoth ebook, they’d go in the running to win a ring from Tiffany’s. Writers had been aware of book-stuffing for months, but this was something else. When #tiffanygate took off on Twitter, Amazon quietly removed Carter’s books from sale.

But close observers of the KU store believe the person behind Carter then returned under another name, Johanna Hawke, allowing another chance to violate Amazon’s terms again. Hawke’s books, about “bad boys and hotties”, are no longer on Amazon – a sign of a ban – but a few are visible on Goodreads. The Guardian has been shown an email promoting Hawke’s books from Starling Publishing Inc, a Canadian company registered to the person believed to be behind Carter.

Carter is not the only scammer banned by Amazon to apparently return under a new name: “hot spicy” romance author Victoria Belle’s books are no longer available on Amazon, but the Guardian has been shown evidence linking Belle to Rye Hart, another author whose books have also been removed - and to one who is currently still active, “reverse harem” romance author Natasha L Black.

Books by Cassandra Dee, previously high in Amazon’s charts and a notorious book-stuffer, were also removed from Amazon last year; last April, an Amazon subsidiary took the British book publisher Jake Dryan and his companies to arbitration, for violating its terms for “combining selections of works they had already published into purportedly new books”, as well as using “clickfarms” to manipulate their rankings.

You are responsible for ensuring that no tactics used to promote your book manipulate the Kindle publishing service Amazon advice to authors

In its advice to Kindle authors, Amazon says that “you are responsible for ensuring that no tactics used to promote your book manipulate the Kindle publishing service”, and that any manipulation “may” result in “termination of your account and loss of royalties”. But as Gaughran points out, the scammers just keep making money. He doesn’t feel Amazon is doing enough.

“When the scamming first started your annoyance is with the scammers, but when it’s still going five years later your annoyance starts to transfer to the people who are supposed to be policing the streets,” he says. “When they moved to this model in 2014 we were worried about scammers, and Amazon said don’t worry, we have robust systems in place to prevent fraud, and it was all bullshit.”

“Part of the reason must be that it hurts authors much more than Amazon. They might see it as only affecting 0.2% of books or whatever, but the top scammers are making over $100,000 a month – money that comes from the author fund, not Amazon’s end. These people gaming the system will roll a huge chunk of that back into advertising too, which either brings readers to the website, or goes directly back into Amazon’s pocket via Amazon Ads.”

Asked for a response to how it polices violations, in particular the cases of Carter, Belle, Hart, and Serruya, Amazon said that it took the problem very seriously. “[We] catch the vast majority of bad actors who attempt to violate our policies before they publish,” said the retailer in an emailed statement. “In the rare instance where one gets through, we employ a mix of automated and human review to identify those books, as well as information received from publishers and from customers. All Kindle product pages contain a link to flag suspicious titles and we investigate all titles and publishers that readers and authors flag.” In regards to Serruya, her novel Royal Love is no longer available for sale, it added.

Don’t blame the ghostwriters

Weak checks … Kindle Unlimited’s storefront. Photograph: Amazon.com

Ghostwriting isn’t anything new: big-time authors including James Patterson have credited multiple co-writers for years, while ghosts carried on series for VC Andrews, and franchises such as Sweet Valley High and Nancy Drew, for years after their original authors moved on. But it has boomed in recent years: searching on Fiverr, the website Serruya claimed she had used, there were more than 80 authors offering to ghostwrite romance novels for minuscule amounts: £165 for 20,000 words, another £60 for 30,000 words of erotica. Sixty-nine more jobs were available on freelance site Upwork, where one employer was looking for ghostwriters to produce stories “in the historical mail order bride romance genre” ($2,300 for 23,000 words). Another was offering $170 for 18,000 words of Amish romance, while on KBoards, which is “devoted to all things Kindle”, a writer was offering buyers “10 Full-Length 50K Novels to Publish As Your Own - $10,000”. As Roberts wrote: “This culture, this ugly underbelly of legitimate self-publishing is all about content. More, more, more, fast, fast, fast.”

There’s a running joke in romance-land about how we might as well have a drinking game every time a plagiarism scandal pops up Shiloh Walker, ghostwriter

Shiloh Walker was alerted to this practice when she saw readers working to identify the lifted passages in Serruya’s books on Twitter. “There’s a running joke in romance-land about how we might as well play plagiarism bingo or have a drinking game every time a plagiarism scandal pops up, because they always follow a pattern,” she says. “First, they deny it. ‘I didn’t. I would never.’ Then they make excuses. ‘My cat died, my mom has the flu.’ Then they disappear. Cris followed this pattern exactly, but she used a new excuse: ‘My ghostwriter did it.’”

That’s when Walker wanted to, in her words, “call bullshit”: “Some people thought ghostwriters were part of the problem and that isn’t the case. There are definitely those who ghostwrite for people who use predatory practices, but legit, professional ghostwriters aren’t the problem.”

Walker describes herself as a “hybrid” author – she does a mix of digital, self, and traditional publishing, with a little ghostwriting on the side. Over the past few years, she has built up a small client list, who provide her with chapter outlines and character sketches, then leave her to fill in the gaps. Ghostwriters who pen memoirs and novels for celebrities will make $20,000 to $40,000 a book, but that’s top of the line; Walker will only say that her ghostwriting income “allows me to continue to write professionally and still pursue my own writing endeavours”.

Most ghostwriters are probably unaware that their work might be being used by scammers, says Walker, although she believes they have a duty to check for plagiarism: “I can’t count the number of times I’ve received ‘requests’ to write a ‘fun and sexy romance in the billionaire sub-genre’ with a word count of 25,000 and I’ll be paid a whopping $250 ... that’s a lousy sum and anybody accepting it is either desperately needing the money, inexperienced or just doesn’t care about the craft and wants the money.”

If buying up cheap ghostwritten content isn’t enough, some scammers are now believed to be buying previously published books and repackaging them to sell as new works, with no disclosure, much to the chagrin of authors like Walker, who has written an open letter to Amazon chief executive Jeff Bezos, pleading for him to address the issue: “They … are flooding KU with recycled works that make the quality of the platform rather questionable, while many authors with new stories, fresh voices struggle to find any visibility at all,” she writes.

A quantity over quality approach works on Amazon; authors who “rapid release” advise that publishing a book every 60 days will position you more prominently in the company’s algorithms, which determine its onsite marketing. There are even guidebooks for this approach: Jewel Allen’s Rapid Release: How to Write & Publish Fast for Profit, explains how to apply “the principles of rapid release, where an author publishes fast to keep readers’ interest”; in Allen’s case, she has published a 50,000-word novel every month.

Roberts is still looking into the situation with Serruya; if the theft reaches the bar of infringement, she plans to sue. “I can afford to while many of her victims can’t. If it’s determined it doesn’t quite reach that bar, I will support every one of my fellow authors she harmed. And I’ll use every resource I can to speak out, to help pull these practices, this bastardisation of the craft, into the light.”

And she has a message for those who are exploiting Amazon’s system, whether it’s through hiring ghosts to churn out books, or plagiarising others. And it’s a doozy.

“Enjoy it while it lasts, because it’s now my mission to turn over the rocks you hide under, then stomp you deep in the muck you breed in. To the black hats who exploit, steal, tutor others to do the same, your day of reckoning’s coming,” she writes. “I swear I’ll do whatever I can, use whatever resources, connections, clout, megaphone I have to out every damn one of you.”