Eruption: Steven Spielberg approached to adapt new Crichton-Patterson novel

Jurassic Park author Michael Crichton died from cancer over 15 years ago - now, his unfinished "passion project", about a humanity-threatening volcanic eruption, has been completed by fellow literary giant James Patterson and is already generating heated interest in Hollywood.

Eruption takes readers on a thrilling journey through Hawaii's biggest island, which, unbeknown to its residents, hides dangerous military secrets dating back decades.

There has been no formal screen auction yet - but Sherri Crichton, who discovered her late husband's unfinished manuscript over a decade ago and controls his estate, told BBC News she was now in talks with Steven Spielberg about a possible big-screen adaptation.

Crichton's earlier works, such as Twister, Westworld and ER, have sold for huge amounts, making him one of the world's most successful book, film and television writers - even in death.

"We have an incredible amount of interest," Patterson told me in a joint interview with Sherri, "including five or so stars who've raised their hands, a lot of filmmakers, studios.

"When Jurassic Park came out, Michael and Steven Spielberg figured out a way to elevate the genre - and it was quite wonderful and different - and I think that's what we're hoping to do with this.

"We have partners in mind where the spirit of this will be not to make just another disaster movie."

Jurassic Park, Spielberg’s highest-grossing film, is now a global franchise worth more than $6bn (£4.7bn).

"We have gone back to Steven," Sherri said.

"What was so magical about it was they introduced things, like what Jim was saying, that have never been put on film before - and that's what this deserves.

"We need this elevated, where you are really taken for that ride like you went on with Jurassic.

"This is that same type of heart-pumping, feeling-chills experience - and to partner with the right team is everything."

Sherri knew Patterson, the world's biggest thriller writer, who has read all of Crichton's novels, was the one she wanted. And after being sent the unfinished manuscript the 77-year-old signed up to complete it.

"I knew that I was in the right hands with Jim," she said.

"Together they were like the perfect duet on the page.

"It was so exciting - and I found myself then sitting, waiting, [thinking,] 'When am I going to start getting the chapters?'"

They had to go through reams of "meticulously organised" scientific research, some so dense Patterson had to hire a researcher, in Alaska, to help.

"It had this dual storyline which is very unusual and they merged," Patterson said.

"I found that irresistible as a storyteller.

"My joke to Sherri was, 'Well, now that I've read this much, I have to find out how the hell it ends'."

And in under a year, this "unprecedented literary collaboration" was completed.

"I really get into these things," Patterson said.

"I'm a ridiculous seven-day-a-week worker."

Patterson has sold more than 400 million books worldwide.

Popular titles include Along Came a Spider, Kiss the Girls and the Alex Cross series, which Amazon Prime Video is adapting for television.

In the UK, Patterson is currently outsold by only Richard Osman and Colleen Hoover.

He is also the most borrowed author in UK libraries, according to publisher Penguin Random House.

Eruption, which had original working titles of The Black Zone and Vulcan, is Patterson's first attempt at posthumous publishing - but he is familiar with high-profile collaborations, having written Bill Clinton and Dolly Parton's autobiographies.

"I do challenge any readers to decide where it was that Michael stopped and I started," he said.

"That was not the easiest thing in the world, to make it seamless."

Sherri has rarely spoken publicly about her late husband.

She was pregnant with their son John Michael when he died, in 2008, aged 66.

As chief executive of CrichtonSun, the publishing and production arm of Crichton’s estate, Sherri has worked hard to protect his legacy.

And in their home in Santa Monica, California, she has kept his writing desk untouched for over a decade.

Along with framed awards and film memorabilia, there are special photos of Crichton and Spielberg together.

Also carefully preserved are all of his original handwritten notes, including first drafts of the Jurassic Park books and films.

Patterson felt pressure to do a good job with Eruption, because of the emotions tied to the project, from Sherri and her son, who loves the novel.

There is enough material for a sequel - or even a trilogy - but neither Patterson nor Sherri will commit to it yet.

In the meantime, completing Eruption has led Sherri and her son to feel closer to Crichton, despite their remnant grief.

"It does ease over the years - but it does still get very emotional," she said.

"I found a part of Michael.

"I already loved him for his warmth and vulnerability and his playfulness and fun and genius.

"I loved him for all of the obvious reasons - and we were starting our family together."

She paused.

"Getting back into his papers was a need to stay connected to him.

"I needed to find a way to answer some of the questions I didn't know how to teach his son about him.

"I didn't want to read it in a book.

"I didn't want to just take it from what people would say their experience of Michael was.

"I needed to know it - and I needed to be able to witness that and feel that - and what happened during that process is really falling deeper in love."

Eruption, by James Patterson and Michael Crichton, is published in hardback by Century, on Thursday, 6 June (Recommended retail price: £22).