Glasgow is cold, but bathed in beautiful sunlight. Sun bounces off the impressive architecture and shines down on shop façades and peoples' faces. On such a lovely day as this, it is hard to imagine the crimes that lurk around the corner. Yet even the thought of the maverick Detective Inspector Rebus (Ian Rankin's fictitious protagonist who daily trawls the dark underbelly of Edinburgh society so vividly evoked in the author's novels) sends a sudden chill down the spine - as it has down the spines of people the world over, gathering his creator an international reputation, his novels found on the world's furthest shores.
I know that Rankin has safely arrived, as his latest tweet announces that he is shopping for vinyl. (The author is a popular and prolific user of Twitter where he tweets under the name @beathhigh). I have followed his tweets for a while, and our paths are soon to meet.
We are here primarily to celebrate the phenomenal work of Oxfam and its relationship with books at the Oxfam Bookfest. "Be moved by the state of the world / outspoken about what's unfair / and excited about making a difference," read the blue posters adorning the Oxfam Bookshop on Byres Road, Glasgow. It is fitting that Rankin is present, for he is certainly a writer moved by the state of the world, and his writing grapples with many injustices. Indeed, as a crime writer, the theme of justice - and its subversion - is at the very heart of his gripping narratives.
It is also a landmark time for the author, now 50. Although looking much younger, his work is filled with wisdom even beyond these years, as his hugely popular novels excavate the darkest recesses of the human mind. Rankin skilfully slots in a sleek overview of 50 years into 50 minutes. With his usual wit he traces the development of his life and literature, movingly evoking his early years growing up in a working-class family in a bleak mining town where he discovered an early passion for both music and books. Born in the Kingdom of Fife in 1960, he graduated from the University of Edinburgh and published his first Rebus novel in 1987. The Rebus novels are now translated into 22 languages and are bestsellers the world over. No stranger to prizes, Rankin is the recipient of four Crime Writers' Association Dagger Awards and has been appointed an Officer of the Order of the British Empire for services to literature.
It is hard to imagine with such a successful writer, but he too had years of struggle as a young writer before his breakthrough book Black and Blue (1997), which, he explains, captured some of the raw emotions he felt about his son's special needs condition. Indeed, it is his favourite Rebus novel, as he finally felt confident that he knew what he was doing after all his previous efforts. "Knots and Crosses I don't like," he confesses, "as it's obviously written by a literature student."
Rankin has long expressed interest in those sections of society who do not read, the reasons that might be, and ways of encouraging them to read. He persuasively discusses the connection between poverty and lower rates of literacy - how eradicating the former would likewise eradicate the latter.
His brilliant new graphic novel, Dark Entries, focusing on the paranormal investigator Constantine, may reach a readership that might not previously have read many books. Rankin sees a particular problem in getting teenage boys to read.
"There are all these different ways to get kids to read now," he says. "I was quite lucky. I had an uncle who ran the local newspaper and he said to my parents: 'It doesn't matter what Ian's reading as long as he's reading.'"
So the young Rankin devoured comic books, which were his early passion.
With such a wealth of experience, he speaks authoritatively on the different ways of telling stories in competing forms, and discusses the relationship between paperbacks and e-books, hardcover books and films. He has never watched the television adaptations of his own work: "I didn't want actors' voices to replace what was going on inside my own head," he explains.
He reveals that the dramatisation of his novels, The Complaints, runs to more than two hours if not three in length. "I've learnt my lesson so I've got executive producer privileges - so I get a say in it. This time, I get to look at the script."
What qualities does it actually take to be a writer? "To be a novelist," says Rankin, with the assuredness of wisdom, "you have to be a sympathetic, empathetic human being, a people watcher." When writing a crime novel, you start with a type then make them more three-dimensional, and you do that through trial and error, through "practice, practice, practice", and learning from the great writers who know how to do it. "Then, you start to find your own voice and own themes that haven't been tackled.
"They say there are only seven plots in the world, but stories keep coming at us," he says. "It's a bit like the 26 letters of the alphabet - out of those, anyone can write a sentence that's never been written before. How amazing is that? You can write a sentence that's never before been written in the history of mankind. I think that's phenomenal. I love that. Stories are inexhaustible because human beings are inexhaustible.
"I'm interested in what makes us tick. Sadly, I'm interested in the kind of darker side of what makes us tick. I would find it harder to write a Mills and Boon or comedy of manners set in a posh English boarding school. I'd much rather write about losers and loners and people who've done bad things along the way."
On the issue of how important his Scottish identity is in his work, he says: "I started writing books about my hometown to make sense of my hometown. For a wee country it seems to be endlessly complex." He realised that the crime novel could be a way of looking at the flip side of the city; not just writing about monuments, but a real, breathing metropolis, with contemporary problems that need to be investigated and talked about.
On the subject of the "infinitely variable sentence", I ask him about Twitter, since he has more than 12,000 followers and more than 4,000 tweets to his name. He explains that, like a lot of folk, he read in the papers about how Stephen Fry was using Twitter when he was trapped in a lift, so Rankin thought he'd sign up for it to see what it was all about. Within a week he had hundreds of people following him and hadn't tweeted a thing. "I thought I'd better write something, or they're following me for no good reason."
It has turned out to be something he now enjoys. "I used to keep a page-a-day diary from the age of 12, till my thirties. My sister every Christmas would buy me a diary and I would fill the whole page even if nothing had happened that day. I use Twitter almost like that. I can scroll back and remember, oh yeah I went to that concert and went to that city and I tweeted today that I was in Mono with my friend having a drink."
It's also been a useful source of information for him, such as when Edinburgh airport was closed during the ash cloud that emerged from Iceland last year. As for Twitter as a novelistic tool, he describes how people are writing novels in 140-character chunks. Rankin himself has written a Twitter-sized story for an Italian magazine, to tie in with an Italian literary festival.
Indeed, the author has been hugely successful in harnessing storytelling for the 21st century, and there is now even a Rebus Edinburgh iPhone app that offers a guided tour from Rankin of landmark locations in his books as well as his own favourite locations, and a host of other audio and video treats.
Back out into the streets of Glasgow, the sun is sinking now, and the air seems filled with the possibilities of infinite stories and infinite ways to tell them.
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