Romance novelist Jasinda Wilder has become the latest self-published writer to land a major deal with a mainstream publisher, after her “dark, sexy” Madame X trilogy was acquired for a seven-figure sum.

Wilder has sold more than 2m self-published ebooks, according to Berkley Books, part of Penguin Random House in the US, which announced on Monday that it would release the first of her traditionally-published novels in November. The publisher, which said it had bought world English rights in print and ebook in the trilogy for a seven-figure sum, described it as an “atmospheric modern-day fairytale about a mysterious woman drawn to two very different men”, with the second and third titles to be released in early 2016.

“Jasinda Wilder has been one of the trailblazing authors in self-publishing. I’m excited she is now partnering with Berkley to release an incredible new series that will thrill her many dedicated fans while also appealing to new readers,” said Berkley vice-president and executive editor Cindy Hwang in the announcement.

The Michigan author, who lives on a farm with her husband Jack Wilder and five children, collaborates with her husband on her novels. “We are about halfway through the first [Madame X] book, and, as with every other Wilder title, Jack and I are working on it as a team. Even when we try to work separately on a project, it ends up being a collaboration,” she told the Bookseller’s FutureBook website.

The Wilder novels now number more than 40, from the New York Times bestselling Falling Into You books, which trace the growing relationship between Nell, who falls for the older brother of her first love Kyle when he dies in an accident, to the erotic Big Girls Do It series, about the curvy Anna’s romance with a rock star.

“I have been sitting on this Madame X story for a while now, waiting for the perfect moment. It’s a special story, with drama, intensity and very sexy characters. Fans have asked for years when they’ll be able to buy a book of mine in stores. This trilogy is my response. It was the perfect opportunity to partner with a traditional publisher to reach the broadest audience,” said Wilder in a statement.

She told USA Today that readers should “expect the unexpected”. “It will still fit within the sphere of style I’ve come to be known for but … more so,” she added. “It’s high concept, which means I’m playing around with some classic tropes, cherry-picking elements from the oldest schools – Rapunzel, Beauty and the Beast, the basic love triangle – and pulling them apart, turning them upside down and inside out, and weaving it all together. Familiar, yet totally new. And the whole will be liberally spiced with angst and steam. That’s the plan, anyway.”

Wilder and her husband are planning to continue self-publishing while releasing her traditionally-published trilogy. “We’ve promised our fans certain titles this next year, and we pride ourselves on keeping our promises, and keeping our readers happy,” she told FutureBook. “We are indies, and we are proud of it. We’ve accomplished a lot as indies, and we will continue to do so as well, but we will now go forward proud to be partnering with Berkley for this project.”