On the surface they wanted people to view Canberra, the city, in a different light. To realise it's not the cold, bland, city of roundabouts that many outsiders think it is. That it is an architecturally stunning city, with landmarks worthy of recognition, a city of sweeping vistas and pockets of hidden beauty.

But they also wanted to reveal some of the secrets that go on behind closed doors in this city of decision makers and  dealers.

And with the release of the third book in the series, The Shadow Game, their vision has been fully realised.

The first two books, The Marmalade Files  and The Mandarin Code, were turned into the highly successful Foxtel series Secret City. Whether The Shadow Game prompts a second series is yet to be seen. Production company Matchbox has the option but no decision has been made. You'll have to read the book to imagine what might happen next.

In the meantime, revel in all things Canberra. From the top of Mt Ainslie on a murky evening, to the rooms of Old Parliament House, to the secrecy of the Chairman's Lounge at Canberra Airport.

It's not just the Canberra places, it's the Canberra people that have made this series special. The transgender character Kim Gordon was based on a real person. The politicians cut close to home. Harry Dunkley could be based on any number of journalists up on the hill.

And while Lewis and Uhlmann insist that it's all fiction, you know they've had some fun doing it.

But when it comes to the fact, the authors have also found Canberra willing to help.

"Canberra is a great resource, it's its own research library and you can find just about anyone in this town or you can find people who can lead you to people," says Lewis.

Lewis first realised this about three years ago when, after driving home from an early morning run on Mt Ainslie, he heard Alastair MacGibbon, now the first Special Adviser to the Prime Minister on Cyber Security, talking on NewsRadio.

"I thought to myself back then, this guy sounds really interesting and when I heard he was from the University of Canberra I just reached out to him," says Lewis.

"He's become a great source of information and he actually launched The Shadow Game for us at Paperchain."

Lewis also names Hugh White as another valuable source, the Australian National University Professor of  Strategic Studies with an expertise in Asia Pacific security issues.

"Just to be able to access these people is a privilege."

More generally he also mentions "all the characters at Parliament House", defence personnel, "talking to snipers or people with actual experience in a particular area that you don't have", to help you "write as accurately as you can within a fictitious setting."

Lewis says it hasn't been hard to sell the idea of a book on the back of the television series.

Fans who have only seen the series may be confused that Harriet has reverted to Harry and ASIO operative Charles Dancer makes a miraculous recovery from having his head splattered all over the forest floor at Mt Pleasant, but you quickly get back onto the plot.

In The Shadow Game, an amount of time has passed since the end of The Mandarin Code. Harry has fallen onto hard times, there's been a change in government, but several of the key characters are still about.

"We wanted to provide a bit of a back story," says Lewis.

"You want people to be able to pick it up, not having read the first two books and hopefully have a reasonable idea as to what's been going on.

"But this one is lot darker than the first two, there's less satire, we had to close the circle on a lot of things. We thoroughly enjoyed the plotting in this one."

Does the darker tone, reflect our darker times?

"You know I'm walking into Parliament House as we do this. I look around and there are guys just over there with assault rifles," says Lewis.

"I can remember when I'd come up to Parliament with my kids when they were young and you could park outside the senate entrance for half an hour and you'd walk through and if you forgot your pass the guard would say, 'Just remember it next time, mate.'

"Nowadays you'd be bloody locked up.

"A darker time? I don't know, it's just a different time."

The Shadow Game, by Steve Lewis and Chris Uhlmann.   HarperCollins. $29.99.