London, UK - British author Sophie Kinsella, who penned the popular Shopaholic series, has died aged 55 after being diagnosed with brain cancer, her family announced on Wednesday.

Madeleine Sophie Wickham, who wrote under the pen name Sophie Kinsella, revealed last year that she was receiving chemotherapy and radiotherapy for glioblastoma, an aggressive form of brain cancer.

"We are heartbroken to announce the passing this morning of our beloved Sophie," her family said on Instagram.

"Sophie counted herself truly blessed – to have such wonderful family and friends, and to have had the extraordinary success of her writing career," her family said.

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She published over 30 books, which have sold some 50 million copies and have been translated into over 40 languages, according to a biography on her website.

Her lighthearted writing style won fans for its humor and relatability, giving an insight into the romances, careers, and financial concerns of young women.

Kinsella preferred the terms "romantic comedy" or "wit lit" over "chick lit" to describe her work.

The first two books from her Shopaholic series were adapted for the 2009 romantic comedy film Confessions of a Shopaholic starring Isla Fisher.

They tell the stories of Becky Bloomwood, a financial journalist who is a serial shopper and hopeless when it comes to her own finances.

"I was really excited, it felt like a new voice," Kinsella said of penning the series in 2000.

"I thought it was my side project. But having discovered comedy, it's addictive," she told The Times newspaper in 2024.

Born on December 12, 1969, in London, Kinsella had five children with her husband, Henry Wickham, whom she met as a student at the University of Oxford.

Kinsella wrote her first novel, The Tennis Party, aged 24, under her birth name, when she was herself working as a financial journalist.

In 2019, her novel Can You Keep a Secret was adapted into another romantic comedy starring Alexandra Daddario.

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Her agents at The Soho Agency said, "Maddy was a once-in-a-lifetime author and friend".

"Maddy was an intelligent, imaginative, loving, and irreverent woman who valued the deeply connective power of fiction," the agents – Araminta Whitley and Marina de Pass – said in a statement.

"She also had an unmatched wit and ability to find the funny side," they added.

Her latest novels were The Burnout (2023) and What Does it Feel Like? (2024).

The latter is a semi-fictional account of her cancer journey that made it onto several bestseller lists.

In an introduction to the book, Kinsella said she had "always processed my life through writing".

"Hiding behind my fictional characters, I have always turned my own life into a narrative. It is my version of therapy, maybe."