I had a sense of déjà vu as I walked through the door of Ian Rankin's home in the well-heeled Merchiston district of Edinburgh. It started on entering the grounds through a wrought-iron gate set into high limestone walls opposite the imposing façade and equally imposing front door. It grew stronger as I entered the airy marbled hallway and nagged away as I chatted to Ian in his capacious sitting room, dominated by a chandelier, hi-fi and baby grand piano.

Where had I seen the place before? Halfway through our interview the answer dawned on me: in Ian's latest book, The Naming of the Dead, the penultimate novel in the Rebus series, when Rebus visits the home of his gangland nemesis Big Ger Cafferty. Even the baby grand gets a mention.

Rankin’s readers are used to his blurring fiction with reality. Real-life crimes, such as the murder of an asylum seeker in Glasgow, are a common source of inspiration for the Scottish crime writer. The Naming of the Dead takes from real life the week of the G8 Summit in Gleneagles last year, a week that began with anti-globalisation protesters on the streets of Edinburgh and Live 8 fans in the fields of Hyde Park, but ended with the G8 overshadowed by the aftermath of the 7/7 bombers in London.

“I decided to write about the summit in June last year,” Ian explains. “The media were saying that there were going to be riots and these extraordinary characters arriving in town – the Rebel Clown Army, the People’s Golfing Association and the Wombles. They then started going on about police numbers and that police would be coming from all over the country. I just started laughing, because I could think of one cop who wouldn't be involved because his superiors wouldn’t want him there, and that was Rebus.”

As usual with the maverick cop, Rebus manages to upset everyone from a Special Branch bigwig to his chief constable after he places himself at the centre of the action when a piece of clothing from a murder victim is found close to Gleneagles. The book is one of Rankin’s best, a heady mix of a complex plot, weaving together global big business, gangster turf wars and activism, with wider questions about whether individuals can make a difference.

The question is close to Rankin’s heart, and he admits he has used Rebus and his sidekick, English sergeant Siobhan Clarke, to work through the issues raised by the summit and the Make Poverty History Campaign. “The reason I write any novel is that I have questions in my mind about the way the world works,” Ian explains. “I just channel those questions through Rebus and Siobhan.”

Recent novels have been increasingly political, covering immigration, asylum seekers and people-smuggling, a point he concedes. “Maybe I am getting more political as I get older,” the 46-year old writer admits. “Or maybe these chances are just too good to miss.”

The new book draws parallels between the overworld of capitalism, especially the arms trade, and the criminal underworld. Both have questionable ethics when it comes to making money. Both treat people like ants.

It is a point not lost on the author.“A few years ago when I made a series about evil for Channel 4 I interviewed a psychiatrist who said that the psychological make-up of a psychopath is almost identical to that of a successful entrepreneur,” he explains. “That is really interesting, that your Murdochs of the world have a pattern of behaviour that is actually quite similar to psychopaths. That has stuck with me and drip-fed its way into a lot of my books.”

Though global politics come off badly in the book, the Make Poverty History campaign does not get it all its own way. Rebus is characteristically cynical about the motivation of some of the Live 8 stars and watches from the wings as Bono and Bob Geldof call for a million people to march through the city. Ian shares Rebus's scepticism about the million people march. “It just didn't happen,” he comments, though his voice betrays relief rather than contempt. “Thank God, because a million people in Edinburgh would have been a complete nightmare.”

Not that Ian disagreed with their objectives. He and his son Kit were among the 250,000 white-clad marchers in Edinburgh on the day of Live 8. His participation explains the authenticity of the protest scenes in The Naming of the Dead: his descriptions of anarchists pursued by police and chanting protesters are vivid and, at times, frightening.

“That whole week in Edinburgh your senses were heightened,” he recalls of the tangible sense of fear that pervaded the Scottish capital. “You walked around and heard police helicopters and sirens all the time. You heard drums and thought a march was going on. Even the letterboxes were shut because they were scared of letter bombs.”

In the end the terror hit London, on the 7th July. He admits 7/7 changed everything and he contemplated ending the book on the eve of the bombings. “When I started thinking about structuring the book I thought it had to end before the Wednesday night, because the bombing changed everything,” Ian explains. “The focus was lost and nobody was paying the slightest bit of attention to what was happening at the G8. All the protesters went home and a lot of the cops went home. But as I started to write, I saw it had to be part of the story.”

The bombings are mentioned in passing, but their occurrence marks a change in tone in the book, as Rebus's quest to uncover the truth about the death of a respected politician who campaigned for the poor, and link it with other murders and a corrupt arms dealer, becomes obsessive. Despite his avowed pessimism, Rebus wants to make a difference, and the thrilling climax suggests the author’s alter ego has helped Rankin reach a conclusion of his own: we may not be able to change the world, but we can make a difference.

It is the penultimate book in the series. Will Ian miss Rebus after he is put out to retirement? Yes, he admits. “I like him.” Any hints about the next book? “I can’t see me bumping him off,” he confides. Then starts laughing, and admits: “As soon as I get back from touring in the first week of November I’ve got to start the last one, because it has to be delivered by the end of May. I don’t have any ideas. I’ve got a title, but no ideas of what it is going to be about.”