Lucinda Riley has sold over 30 million books worldwide.
The seventh part of her series about the seven sisters, The Missing Sister, was published in Swedish at the end of May this year.
"It is with great sadness that we must tell you that Lucinda passed away peacefully this morning, surrounded by her family who were so important to her," the family wrote in a statement.
Sold worldwide
Riley was born in Ireland and previously worked as an actress.
At the age of 24, she wrote her first book.
Her novels have been translated into 37 languages, writes the publisher Bazar.
Lucinda Riley fell ill with cancer four years ago.
When The Missing Sister was released, the publisher wrote that Riley had planned to continue the book series.
Last year, five of her books made up half of the top ten on the list of most listened books on the audiobook service Bookbeat.
The Seven Sisters is a mysterious story about adoptive sisters and spans time and space.