What’s it like being a fantasy writer? Well, according to Glasgow-born novelist Martin Stewart, possibly not quite as well paid as people think. “The perception is you get JK Rowling money which is really not the case.”

Not yet anyway. But who knows? Because Martin is one of the bright new stars of British young adult fiction. His first novel Riverkeep has just been published and has already seen his publisher Penguin Books offer giddy comparisons to such successful writers as Neil Gaiman, Patrick Ness, Philip Pullman and even Charles Dickens. He was given a deal on the basis of just a 2000-word short story that became the opening chapter of the book.

This is not the norm. “It’s incredibly rare for us to commission a book from an unknown author on just 2,000 words,” Penguin’s publishing director Shannon Cullen admits, “but Martin’s writing is so arresting – dark, atmospheric and accomplished – that the entire editorial team was seduced. In those few words.”

Martin, 33, lives in Troon but he’s originally from Clarkston in Glasgow. And although Riverkeep is set in a fantasy landscape you don’t have to look too hard to find echoes of the city of his birth in its pages. The city of the novel, Oracco, has the same boundary outlines as Glasgow, the coastline of the novel looks an awful lot like the Clyde Estuary and the river of the title could be the Clyde by another name.

“And I hope,” Martin adds, “that the voices and certainly some elements of the characters would be recognisably Scottish and maybe particularly Glaswegian; a cheerful belligerence where people can insult each other with a smile and take it in good spirits. And a kind of good-natured dry resilience and humour.”

Riverkeep tells the story of Wulliam, a 15-year-old boy who helps his father pull bodies from the waters until the day the body he pulls from the water is his own father’s. Not that his father is dead. Or not quite.

It’s a book full of monsters and magic but it’s possible readers might be prompted to think of George Parsonage, chief officer of the Glasgow Humane Society, who has been recovering bodies from the River Clyde since he himself was a teenager.

When Martin first read a newspaper article about George he knew he had found something he could write about. “George had been 14 when he first went out with his father for a recovery from the river which seemed extraordinary to me. I couldn’t do it now as a 33 year old.

“It seemed unbelievable that no one had written that story before.”

So when Martin sat down to write the book at the beginning of last year he paid George a visit.

“I took him some Hobnobs to grant me safe passage and he made me a cup of tea and told me amazing stories. What a life he’s had. It’s extraordinary. He might be the most physically strong man I’ve ever met. It’s like he’s carved out of wood. He spends his whole life rowing. He’s an impressive figure. The idea of the river is in his blood.”

The book has another sadder source of inspiration too. In 2010 Martin’s grandfather James Gray died. He’d been a robust Glaswegian who had in his later years suffered from cancer, Parkinson’s and dementia. Martin and his family had watched James waste away not only physically and mentally

“To have the experience of having someone vanish on you while still in the room is an extraordinarily difficult, probably quite modern challenge,” Martin admits. The experience, as well as the example of one of his favourite fantasy writers Terry Pratchett, prompted an interest in the late Margo MacDonald’s right-to-die parliamentary proposals.

“It’s a hugely complex issue,” Martin accepts. But, he adds, “I wonder if in a couple of hundred years’ time we will look back at the way we now pump medicine into people to their detriment.”

It might seem strange to use fantasy fiction – and young adult fantasy fiction in particular – to study themes of grief and the loss of fathers. But Martin is adamant that it is actually the perfect vehicle.

“Genre allows you to create a form of storytelling that makes these things not even more comfortable, but more readable. It allows people to feel safe while reading it.

“It’s why kids can read books about things that challenge their fears or ideas. I think books are the best ways of wearing somebody else’s skin and building empathy.”

Martin has always been a keen reader, probably, he says, because his parents wouldn’t let him have a TV in his bedroom.

After it became clear that he was never going to become a professional footballer, the idea of becoming a writer started to appeal to him in his late teens. He would write between day jobs that included working as a golf caddy and as a barman. But at 25 and with no signs of getting published, he retrained as a teacher and found something he loved.

He might still be teaching at Kyle Academy in Ayr if he hadn’t broken his kneecaps whilst playing football. In his recovery time he wrote the story that prompted the book deal.

“I do miss teaching. The best parts of it are amazing.

“That high-energy environment has been replaced by me sitting at home in my shorts avoiding Homes under the Hammer and wondering if I’ll shower. It’s a very different pace of life.”

Riverkeep by Martin Stewart is published by Penguin Books, priced £7.99