Anna Snoekstra's Mercy Point, published last year, is based around Katoomba and Echo Point, and references annual events such as the Winter Magic Festival.

It also travels deep into a cave system, inspired by the magnificent Jenolan Caves.

Raised in Canberra, but living in Melbourne for 12 years now, Snoekstra would often visit the Blue Mountains as a child during school holidays.

"There was always something so magical about it," she said.

As an adult she returned for a writers' residency at Varuna, the Writers' House in 2017, where she worked on a draft of Mercy Point, and would wander around the streets of Katoomba, deciding where her characters would live.

"People living in the houses were like 'why does this girl keep walking past our house and staring in,'" Snoekstra recalled.

"For me the setting is the most important thing. I came from the place that you need to be able to navigate the place."

Mercy Point is about five teenagers with one big thing in common; they are all sure they're adopted. They must decide whether to continue living a lie, or come together to hunt down the truth, no matter how dangerous that might be.

READ MORE: Gardens of Stone plan: Lithgow's mining, tourism industries to coexist

The real story of their parentage is more terrifying than they could ever have imagined, in a secret that goes right to the very heart of the town itself.

One of the places the teenagers meet is at the hotel run by one of their parents, which is based on the Echo Point Motel.

But after the first draft the author decided to remove the Katoomba town name, as readers were getting confused between fact and fictional events.

"Readers read the draft and said 'is this true, I don't remember there being a cave-in in Katoomba,'" Snoekstra said.

The Winter Magic Festival also makes its way into the book.

"I like the idea that it was set in the middle of winter and the mistiness that takes over the place," Snoekstra said.

Unlike the typical portrayal of Australia with a coastal or outback summer setting, the author was keen to portray a different side of Australia.

READ MORE: Lithgow TAFE introduces Western Connect Program for remote learning

"It's really nice to get this Mountain town version of Australia in the middle of winter," she said.

She also visited Jenolan Caves to get a good idea of what a cave system looked like, which was crucial for the latter part of the book.

But this presented its own complications, as the author is claustrophobic.

"Going down into the dark sounds terrifying, so I really wanted to write about that. Then when I was there I thought I really have to experience it myself, so then I had to face my own fear in order to write about it," Snoekstra said.

"But it was really beautiful down there and really special." 

Mercy Point could be turned into a film or TV series and set in the Blue Mountains.

There have been discussions with Screen Australia, and Snoekstra's been working closely with Australian producer Marie Maroun, who has worked in the US for a number of years and has returned to Australia and is keen make Australian content.

"We are in development at the moment, but hopefully we'll be able to actually visually create the film in the place that it's set," Snoekstra said.

She doesn't envisage it being too difficult to film at a high school and around Katoomba's streets, but the cave system would have to be built as they couldn't film in Jenolan Caves. 

READ MORE: NAPLAN, 2018 results: Top performing schools revealed

It's not her first book destined for the screen. 

Snoekstra's debut novel Only Daughter, published in 2016, was picked up by Universal Films and will be Americanised and set in Arizona. 

Screenwriter Erin Cressida Wilson, who adapted Paula Hawkins' best-selling novel The Girl on the Train, will also adapt Only Daughter for film.

"She's such an amazing writer, so that's actually quite exciting and she really knows what she's doing for the screen so it will be really interesting to see it become something," Snoekstra said.

"She will still take my characters and my concepts and the story, but see it in a totally different angle. Film is such a different art form to a novel and I think that's OK for it to be quite different."

Snoekstra has also written crime fiction, but she loves young adult fiction and the sense of hope it brings.

"The one thing that seems to pervade through young adult fiction is that sense of hope and hope for the future, and I found that to be the most important thing to focus on right now in these times," she said.

"The kind of political climate we are in at the moment we are in such a strange situation, and there's a strong feeling of hopelessness and people worry about the future and also climate change."

Snoekstra's 30, but regularly mixes with teens when she volunteers at the 100 Story Building literacy centre in Melbourne. Here she co-ordinates the weekly writers' club, where they have written and produced their first audio play.

She also finds it easy to tap into being a teenager​.

"My true self I feel like is a 15 year old girl. It feels really natural and really right for me to write about that age," she said.

"When you're younger, everything is new and really raw, and you're experiencing all these things for the first time. It's such a rich area to write about and it really brings you back to when you were at that age.

"To me at least, friendship just meant everything to me when I was a teenager."

Whereas some young adult books like to focus on love relationships, Snoekstra preferred to focus on friendship. 

"I wanted to prioritise how important friendship is and new friendships and how they can totally change who you are."

Snoekstra is currently hard at work on a sequel to Mercy Point and there could be a prequel in the wings as well.

She released her second novel, Little Secrets, in 2017, and the twisty and suspenseful The Spite Game came out in 2018.