Jilly Cooper, who captured millions of readers with her raunchy tales set amid horse-loving high society, has died at the age of 88, her agent has confirmed.

The author, whose 18 novels include Riders and Rivals, “defined culture, writing and conversation since she was first published over 50 years ago,” said her agent Felicity Blunt. “You wouldn’t expect books categorised as bonkbusters to have so emphatically stood the test of time but Jilly wrote with acuity and insight about all things – class, sex, marriage, rivalry, grief and fertility.”

Cooper died on Sunday morning after a fall. “Her unexpected death has come as a complete shock,” said her children Felix and Emily. “We are so proud of everything she achieved in her life and can’t begin to imagine life without her infectious smile and laughter all around us.”

In a statement, Queen Camilla said that “very few writers get to be a legend in their own lifetime but Jilly was one, creating a whole new genre of literature and making it her own through a career that spanned over five decades … may her hereafter be filled with impossibly handsome men and devoted dogs”.

Cooper is best known for the Rutshire Chronicles, which follow the scandals of the upper classes in the fictional Cotswolds county of Rutshire. The second novel in the series, Rivals, was adapted for Disney+ and released last year.

While her novels were often described as “bonkbusters”, to her they were “a bit of everything”, she told the Guardian in 2016. “But if they want to call it bonkbuster they can – except it ought to be called ‘shagbuster’ now, bonk is out of date.”

Cooper was born in Hornchurch, Essex, in 1937, and attended Godolphin School in Salisbury, Wiltshire. She began her writing career in journalism as a cub reporter on the Middlesex Independent in 1956, before moving into PR.

In 1961, she married publisher Leo Cooper, who had proposed on their second date. “After an ectopic pregnancy, it became clear I was going to be unable to have babies myself,” Cooper told the Guardian in 2017. “I was in a state of shock. I felt I’d let Leo down. But we were encouraged to adopt. I was 31 when we adopted Felix, and Emily came into our lives three years later.”

In the late 60s, she began writing columns for The Sunday Times, before moving to the Mail on Sunday in 1982. Her first book, the nonfiction title How to Stay Married, was published in 1969.

Cooper’s debut novel, Emily, was published in 1975, the first of a series of romances based on magazine stories she had published. Bella, Imogen, Prudence, Harriet and Octavia would follow, plus a collection of short stories, Lisa & Co, in 1981.

The first of 11 instalments of the Rutshire Chronicles, Riders, was published in 1985, followed by Rivals in 1988. Riders and a later book in the series, The Man Who Made Husbands Jealous, were adapted for television in the 90s.

Former prime minister Rishi Sunak, famously a fan of the author’s works, wrote in a statement on X: “Sad to hear of the passing of Dame Jilly Cooper, a storyteller whose wit and love of character brought joy to millions. My thoughts are with her family and fellow readers.”

Along with her adult novels, Cooper wrote several books for children about a mongrel, Mabel, and many nonfiction titles including Class, her 1979 book about the English class system.

She was given a damehood in the 2024 new year honours list for her services to literature and charity. “I cannot believe I am a DBE, which in my case also stands for ‘delighted, bewildered and ecstatic’,” she said at the time.

“With a winning combination of glorious storytelling, wicked social commentary and deft, lacerating characterisation, she dissected the behaviour, bad mostly, of the English upper-middle classes with the sharpest of scalpels,” said her publisher Bill Scott-Kerr.

“It is no exaggeration to say that Riders, her first Rutshire chronicle, changed the course of popular fiction for ever,” he added. “Ribald, rollicking and the very definition of good fun, it, and the 10 Rutshire novels which followed, were to inspire a generation of women, writers and otherwise, to tell it how it was, whilst giving us a cast of characters who would define a generation and beyond.”

While Cooper’s funeral will be a private service, a public event will be held at Southwark Cathedral in the coming months, with details due be announced.