How I created Scotland's answer to Fifty Shades Of Grey

"I actually had a discussion with one my friends about what is expected now," says Young, between sips of latte. "Television shows, films and books can be so graphic. I asked her: 'How far is too far?'"

It's a good question and one that Young, 26, will have to get used to as her debut novel hits bookshops next week. On Dublin Street tells the story of a young American woman who moves to Edinburgh's New Town, where she is swept off her feet by a passionate love affair with a dashing property developer. The gloriously racy content has already seen her dubbed Scotland's answer to Fifty Shades Of Grey author EL James.

The book has been a hit in America, beating JK Rowling's latest, The Casual Vacancy, to No.1 in the Kindle US charts, and topping the New York Times and USA Today e-book bestseller lists. Young subsequently landed a two-book, seven-figure deal from Penguin and is working on a sequel, Down London Road.

However, for now, she's having to endure my clumsy questioning. Young laughs heartily when asked about the, ahem, nature of any hands-on research. She admits to some semi-autobiographical detail ("Jocelyn is quite a personal character. Her experiences and characteristics come from me, friends and family – albeit an exaggerated version") but she's not telling how that has shaped her raunchy prose.

"It was mostly things I knew and from friends' stories," she says. "Reading other adult contemporary romance too helped me understand the 'levels'. Some of the language was very flowery and I didn't want to go down that road. I wanted it to be realistic."

Still, I'm curious about the reaction of friends and family: have her parents seen the book? "My dad? God no - My mum has read it but she skipped all the 'naughty scenes' as she calls them," says Young. Did she give her mother a long list of pages to avoid? "I didn't have to. When she got to one she would flick ahead saying, 'No, no, no,' until she was past," she smiles. "Reading it on her Kindle made it easier to bypass the bits she didn't want to see, but once she skipped too many pages and ended up on another sex scene." Young fights back a giggle. "She said, 'Oh, my God, aaaargh,' and fumbled to get away from it again."

I tell Young that Irish chicklit pioneer Marian Keyes once told me her father was unable to make eye contact for the best part of six months after reading the bedroom scene in her debut novel, Watermelon, (curiously, her mother had no such qualms but steadfastly refused to believe oral sex existed: "She thinks it's this kind of mythical thing like a unicorn.")

Young hoots with laughter. "It's not the kind of conversation you want to have with your mum," she says. "My gran was the biggest surprise. She told me: 'I've read worse.' I was like: 'Wow, OK, Gran.'"

Falkirk-born Young, who has already written and self-published 10 young adult novels, released One Dublin Street online in August. Within a fortnight she was at number 16 in the US Kindle charts, had signed to a literary agent and landed a deal with Penguin.

While on paper it appears an overnight success, the Edinburgh University history graduate has put in some hard slog: "I spent five months researching self-publishing before deciding to finally go for it. I was jobless, so reckoned I had nothing to lose."

That was February 2011. Over the following months she self-published four young adult fiction novels. By May that year she saw sales start to take off. "The way it works is that you don't get paid until two months after you make the money so it wasn't until August I realised I could write full time," says Young. "After university I had worked as dispatcher for a taxi company. I also had a part-time job as an admin assistant with the police but they paid me off due to budget cuts.

"Then I got a temporary job working at the courts, but that only lasted a few weeks. I sent out letter after letter, email after email for job interviews but was getting nowhere. It was disheartening."

But as Fifty Shades Of Grey took off, Young had her own lightbulb moment. She had been toying with writing adult contemporary romantic fiction and already had the idea for a heroine – the feisty and forthright Jocelyn Butler, a fledgling writer who has fled her troubled past for a new life in the Scottish capital – and decided it was worth a shot.

When I ask her about that quote, she fiddles nervously with a bracelet, smoothing down some non-existent creases in her dress. "It came from the loss I've suffered in my own life," she says. "I lost my elder brother when I was six. A couple of years ago my other brother, David, was diagnosed with a brain tumour and I had to watch as he fought through that. I've had to deal with lot of grief and a level of PTSD [post-traumatic stress disorder]. I suffered badly from panic attacks for a long time."

Authors aren't always keen on the word cathartic, but for Young the book provided a release. "It was my way of getting it all out, although I didn't realise it at the time," she says. "Every year, without fail, on the anniversary of my brother's death I would have a bad panic attack. Since writing the book I haven't had any. The anniversary passed this year without one. It has made me take a step back and look clearly at my own life."

Her brother Robert was 12 when he was knocked off his bike and killed by a drunk driver in 1992. "We were close," she says. "If there hadn't been a six-year age gap, everyone would have sworn we were twins. We looked alike, had similar personalities and loved the same things. If he was alive today I know we would have been close."

Asked about her memories of that time, a tremble creeps into her voice. "We had an argument and I never said goodbye to him that morning," she says, trailing off. There's a silence as a large tear rolls down her face. Young wipes it away, shaking her head. We stop and regroup.

A few minutes later, after repeated unnecessary apologies, Young is back on steadier ground talking about her family today. The first thing she did, she says, when her cheque for that seven-figure deal arrived, was to surprise her parents – Alexander, 52, a lorry driver, and Elaine, 50, a retail assistant – and brother David, 30, who also drives HGVs.

"I paid off their mortgages," she says, proudly. "It was something I wanted to do, but more emotional than I expected. I wrote cheques and put them in cards. We had all been out for dinner to celebrate my book deal and went back to my flat afterwards where I handed them over. Everyone started crying. My brother's fiancee started first, then everyone else. It was like a chain reaction. I had to leave the room. It was an amazing moment."

What about herself? Any big blow-out purchases, I ask (thinking yachts and mansions)? "I did buy a Ted Baker dress," she says, looking thoroughly delighted, going on to add that she's perfectly happy in her modest rented flat in Bridge of Allan, Stirlingshire.

When it came to laying bare elements of her own life, Young says she wanted the book, although fiction, to remain true to her experiences. "I've already had emotional emails from readers," says Young. "There was one woman who had lost her entire family and said she had never read a book before that got her like this. Another had recently lost a baby and said it was exactly what she needed to pick herself back up."

Yet, Young admits she shied away from confronting her own grief. "I was stubborn," she says. "When I was younger I saw a doctor who suggested talking to someone, but I didn't think a therapist could tell me anything I didn't already know.

"As a teenager I was introverted and painfully shy. Then when I turned 15 or 16, I don't know what happened. I think perhaps I decided I'd had enough of people walking over me. I also had a great teacher who taught me how to feel less self-conscious about being" – she trails off, smiling – "well, completely and utterly nuts. I got more confident. I realised that, if you don't stand up for yourself, people will walk over you."

Testament to Young's tenacity is a tattoo on her back which she got at 19. "It's the symbol for the word samurai and a reminder to myself that life is a bit of a battle," she says. "The only ones that make it through are warriors. I'm a huge fan of The Killers and their latest album, Battle Born, has been a huge inspiration. There is one lyric: 'Cut from the cloth of a flag that bears the name: Battle Born,' and I was thinking of getting the words 'battle' and 'born' on either side of my tattoo. Although that might just be asking for trouble."

Yet for all her candour and verve, Young is less at ease with the notion of potentially being held up as a role model for other young girls. "I'm not comfortable with that kind of thing," she says. "I never set out to be a role model or anything particularly meaningful. I just wanted to write a book people will hopefully enjoy and relate to."

She admits the frothy EL James comparisons are inevitable, but while Fifty Shades Of Grey features a submissive wallflower of a female lead, her own literary creation most definitely wears the trousers ("I had a shoe box of vibrating goodies that took care of me when I was in the mood," heroine Jocelyn boldly declares).

Leading man Braden Carmichael is based on the typical Scottish man, she says – "blunt, straightforward and cocky" – before hastily adding, "But he is also very much a fantasy character, this unbelievably intuitive man that all women wish they could find." So there's no real-life Braden, then? "Unfortunately not," she says, wryly.

With EL James reputed to have sold her trilogy's movie rights for a cool £3.1m, Young has already tongue-in-cheek earmarked an all-star cast should On Dublin Street follow suit. "Even though he's blond rather than dark, I'd love the Australian actor Chris Hemsworth to play Braden. He's attractive but rugged too – we could always dye his hair," she jokes. "Jennifer Lawrence would be perfect as Joss, Rosamund Pike to play Braden's sister Ellie and James McAvoy as his best friend Adam."

Fifty Shades Of Grey was credited with spicing up the nation's ailing sex lives. Does Young hope to do likewise? "I have had emails saying, 'My husband says thank you,' so that's quite funny." What about an On Dublin Street-inspired baby boom? Another thunderous laugh. "We'll have to wait and see," she says, eyes twinkling. I guess we'll know in nine months' time. n

On Dublin Street by Samantha Young is published by Michael Joseph (Penguin UK) on Thursday, priced £7.99. The author will be doing readings and book signings at Waterstones on George Street, Edinburgh, at 6pm on Thursday and Ocean Terminal, Leith, at noon on February 2.