Unlike many authors, Cullinane never had a burning ambition to write the Great New Zealand Novel.
"It's funny, really - the same year I publish my first book I'm eligible for the Gold Card."
His interest in fiction was bolstered by the oil rigs' libraries and the movie thrillers shown nightly.
One gets the sense that if his age hadn't disqualified him when he tried to return to the oilfields just a few years ago, he'd still be there.
That he isn't is great news for lovers of smart crime fiction. Not that the success of Red Herring has changed his day-to-day routine: mornings you'll find him pounding the streets of Mt Roskill, delivering mail.
After a stint at TVNZ and helming a critically lauded film (2007's We're Here To Help about Christchurch property developer David Henderson's run-in with the IRD), Cullinane enjoys the relatively stress-free job. There's plenty of time to think up plot-points and job security apparently isn't a problem.
"We have a very strong union."
And unions - their power and demise - are at the heart of his book, the bulk of which was written while Cullinane was enrolled at the University of Auckland's creative writing course in 2012, under poet John Newton.
The manuscript landed on then-HarperCollins editor Finlay Macdonald's desk in 2014 and was swiftly snapped up.
No surprise. Red Herring is an enormously confident and accomplished debut. Its plot is built around the 1951 Waterfront Strike - the largest industrial dispute in New Zealand history - but is never a slave to it.
His touch is light, even managing to sneak in that old pot-boiler stand-by, gelignite on a railway track. Think James Ellroy's LA Quartet but gentler, sans the megalomania.
The drama of the period - red paranoia (McCarthyism was in full swing), the Korean War -- and some of our left's larger-than-life characters create a compelling setting.
But for Cullinane, capturing the dialogue was key.
I think when the history of the last 30 years is written, one of the fascinating things that'll emerge is how a country that had such a strong union presence lost it all almost overnight
"With characters like Jock Barnes and Sid Holland I tried to find things they'd said in real life which gave a sense of their personality," he says.
"Jock's 'pure bumkum from end to end' and Sid's 'I'm the Prime Minister - I can't get any bastard to shine my shoes' for example.
"I thought people who say things like that are probably like this... and went from there. With Fintan Patrick Walsh it was easy to look at his photograph and get a good idea of the sort of man he was, and easy to extrapolate from the things he was believed to have done to even worse things he might well have done. His malevolence aside, Walsh had a life of high adventure."
When researching the book he found a photo of Barnes and several other wharfies outside an Auckland Town Hall stopwork meeting in 1950.
"There's the hats and broken noses, big jackets. These guys have been through the Depression and at least one World War. They're in their 40s but there's still fight in them. I wondered what would they make of New Zealand today when all that stuff - the unions for the most part - has gone?
"I think when the history of the last 30 years is written, one of the fascinating things that'll emerge is how a country that had such a strong union presence lost it all almost overnight."
And don't get him started on Richard Prebble.
Cullinane quotes The Godfather's Balzac-penned epigraph, "Behind every great fortune is a great crime," when describing Red Herring's villain - Walsh, a man the late historian Graeme Hunt described as "the nearest thing New Zealand had to an American-style industrial gangster."
Walsh blazes through the pages of Red Herring. While his author's note - "where the facts have interfered with the story I've changed the facts" - gives Cullinane licence, none of the writer's fictive musings sound out of character when it comes to the union leader.
"He was a fascinating man," says Cullinane. "And one with a murderous reputation. He went to California and worked with the IWW - a very strong union then - and they had wars with company detectives who worked for the big mining companies.
"Walsh is supposed to have shot one of these detectives, which is why he left America and went to Ireland. When he came back to New Zealand he had a new name. He knew the prime ministers of the time and carried a lot of power.
"The great fortune was the money to be made by New Zealand farmers selling wool to the Americans for the soldiers in Korea. Suddenly they could pay off their farms overnight. That was threatened by these - as they saw it - reds trying to shut down the wharves.
"So they went to considerable lengths to ensure that didn't happen."
Cullinane sets his hero, disillusioned private detective Molloy, loose in the corrupt, shadowy world of Auckland's political power-players. He reckons Robert Mitchum would have been perfect to play him in film version. Kate Winslet will do for the love-interest, Auckland Star cadet reporter Caitlin O'Carolan.
Cullinane believes the period was the start of a descent into neo-liberal capitalism - Cameron Brewer gets a wry mention - and cites the Kelly Gang, "a lot of self-satisfied conservatives who thought they ran the country from the soft leather armchairs of the Northern Club," as forerunners of the bully-boy corporate culture he sees holding sway today.
Cullinane's fascination with larger-than-life figures is set to continue. He's written the script for his next project, a film based on a true story about a man in Mangakino.
"This guy was a failure at everything he tried except one thing: he ran the most efficient fire brigade in the country. It was so efficient that the Fire Service shut it down.
"So what did he do? He started lighting fires to get his job back."
