So this is the end, then. Well, perhaps not quite. Exit Music, the much trumpeted latest work from Ian Rankin sees his world famous cynical copper Detective Inspector Rebus handing in his warrant card for the last time and retiring permanently to the back room of the Oxford Bar. But while, by the end of Exit Music, Rebus is no longer officially in the employ of Edinburgh CID, it’s not giving too much away to say that the door to the possibility of further Rebus books remains ajar.

‘I honestly don’t know if this is the last Rebus book or not,’ says Rankin over coffee in the living room of his house in Edinburgh’s leafy Merchiston.

‘It feels as if there’s unfinished business there between us, so maybe it’s not all over. I could leave it at the end of Exit Music, that might be a decent end, but I really don’t know.’ In keeping with Rankin’s last few Rebus outings, Exit Music focuses on the burgeoning political and economic powers based in Scotland’s capital post-devolution, this time the death of a Russian poet implicating extremely rich foreign businessmen, high-ranking bank officials and power-hungry politicians in a far-reaching conspiracy.

‘This book was kind of about where Scotland might go in the future,’ Rankin says. ‘If it goes independent, does a small country heading for independence attract the wrong kind of folk? The ones who are only after making a quick buck? What happens then?’

Fans hoping for a bunch of loose ends to be tied up at the end of the 17th Rebus novel in 20 years are in for a disappointment, not least in the Jekyll and Hyde relationship between Rebus and his nemesis Big Ger Cafferty, which is left dangling on the very last page. As the series has progressed down the years, both the city Rankin is describing and his own writing style have grown in complexity and confidence, to the point where the author barely recognises the city and characters of the early books.

‘They’ve changed loads,’ he admits. ‘The first book, Knots and Crosses, in some ways is a complete disaster area. To my mind, it’s too obviously written by a post-graduate English student. I mean, Rebus quotes Walt Whitman, and he reads Dostoevsky too. He’s too much like me in that first book.’

One thing for sure is that Rankin is leaving Rebus alone for at least the next wee while. As well as all his promotional commitments for Exit Music, which stretch to the end of the year, he’s struggling with a graphic novel, Hellblazer (‘I’m three pages in, it’s harder than I thought’), beefing up a New York Times fiction serial into novelistic form, and has signed up to a two-book deal for unspecified non-Rebus adventures. So if this really is the end for DI Rebus, what does Rankin think the series leaves as a legacy? ‘Really, all I’ve tried to do is write about contemporary Edinburgh, which no one seemed to be doing when I started. Historians can hopefully come back in the future and get a sense of what the city was like in the 80s, 90s and 21st century. That’s pretty much all I can hope for.’

Exit Music is published by Orion on Thu 6 Sep. Ian Rankin is at Eastwood Park Theatre, Glasgow, Sun 9 Sep.