Collins -- who refuses to reveal how old she is, except to say that she is still several years shy of 70 -- released her 26th novel, "Married Lovers," in the United States on Tuesday.
"I get the 15-year-olds all the time going 'I read my mum's book under the covers and you taught me everything I know about sex,"' Collins said of e-mails she receives, adding married couples also thank her for spicing up their love lives.
While disliked by critics, the younger sister of Hollywood actress Joan Collins has sold more than 400 million books in more than 40 countries and all of her previous 25 novels remain in print, according to her publisher St. Martin's Press.
"I'm a storyteller. I'm not a literary writer and I never pretended to be," Collins said. Many of her novels have been made into hit television movies and mini-series.
During an interview in a luxury New York City hotel suite, she told Reuters she is "horrified" by the fact it has been four decades since her first novel, "The World is Full of Married Men," was published in the United States and Britain.
"It's ridiculous, time goes by so fast when you're having fun. I think I am the only writer still on the bestseller list all these years later," said Collins, who still handwrites her novels on yellow legal notepads.
Her debut novel, reportedly deemed "filthy and disgusting" by author Barbara Cartland and banned in Australia, she says, "was way before its time" with its tale of a woman who cheats on her husband and another who likes sex with married men.
The latest offering from the Beverly Hills-based author follows a story involving three high-powered Hollywood couples, two affairs, one underage Russian ex-prostitute and a murder.
A self-confessed pop-culture junkie, Collins said she pulls all her stories from "real life and it's toned down."
"All the characters I write about are really characters that I know, I've seen, I've observed," she said.
She began writing when she was just 8, picking up her talent for love scenes after secretly reading her father's copy of "Lady Chatterley's Lover," which Collins says was kept in a brown paper bag beside his bed.
"It's my passion, it's my hobby, it's my everything. I just love to write," Collins said. "I'll write 'til I'm like 100 and whatever and I will drop with a pen in my hand going 'And he looked into her eyes and it was..."'
Michelle Nichols for Reuters