If you've ever read anything by Dapin, often accompanied by his rather incongruous headshot, you'll understand what he means. As a long-time columnist for Good Weekend magazine, his byline photo showed him unsmiling, arms folded, lots of tattoos. But his writing was often raw, moving, personal and perceptive. The image might have conveyed a certain menace, but in person he's wry, light-hearted and generally self-deprecating.

Dapin is also known for a certain memoir he published in 2004 about his time as editor-in-chief of Ralph magazine. Sex & Money was a rollicking – and acutely self-aware – account of what went on behind the closed doors of a lad-mag that mainly featured naked chicks. But in the decade or so since, he's written several books, including three novels, and won or been nominated for a clutch of awards.

Why, then, does he maintain that he has finally reached "peak boring", in accounting for his current fascination with military history and the Vietnam War? You'd think there would never be a time when war stories, and written accounts of said stories, would not interest large segments of the population. But what Dapin is really referring to is his trajectory as a writer.

"I think as you get older, you can get more and more boring, and in men this manifests itself in an interest in military history. In women it tends to be gardening," he says, although his accompanying guffaw indicates that he's well aware this is a silly (and maybe accurate) generalisation.

This fascination has manifested itself most recently in a pair of books – one non-fiction, and the other a novel – about the Vietnam War. Nashos War is an account of Australian servicemen in Vietnam, while R&R is a brooding military police thriller. But in fact, war is a theme that has cropped up in much of his writing. His 2011 novel Spirit House, long-listed for the Miles Franklin Award, was about a survivor of the Thai-Burma railway. This led to a commission from Penguin to edit an anthology of Australian war writing.

It was while he was immersed in collating first person accounts of Australians at war, from colonisation to Afghanistan, that he realised there was a noticeable lack of good first-person narratives of Vietnam, particularly of national service experience.

It was partly, he says, because not as many Australians had been involved in the Vietnam War, and partly because there were fewer diaries and letters to work from.

"What used to happen in Vietnam was you'd go to Hong Kong or wherever … and buy an American reel-to-reel recorder," he says.

"Rather than write a letter, they'd make a reel-to-reel recording, then send it back to their parents at home or their girlfriend, and then their girlfriend would record over their recording with their response and send it back. So a lot of this source material that would ordinarily have fuelled memoirs is missing from the Vietnam veterans."

This paucity of material is not news to historians, who have been grappling with the advent of modern technology when it comes to collecting war narratives.

"It's a big thing in military history now, because what's happening now is people aren't writing letters, they aren't even writing emails – they're Skyping home from Afghanistan … and I suspect now from Iraq," he says.

"So it's all lost. That tradition of trench diaries and letters from the front is gone, and it's a concern for historians today that began I guess with this tape thing in Vietnam. It's just easier. I doubt very much many people wrote because of a love of words, they just wanted to communicate what was happening to them, and it's an easier way to do, and on Skype they can actually see the people they're talking to, which must be a great comfort to them."

There was also a period where publishers weren't searching for Vietnam War narratives, and those who went probably didn't write much anyway.

"It's a massive generalisation, but many of those who went, they tended to be very sporty, athletic people. It was the footy team that went to Vietnam, not a dux of English, if there is such a thing," he says.

And of the 60,000-odd Australians who were called up to the National Service, the 15,300 who eventually did serve were chosen for their physical attributes, rather than the ability to put pen to paper and record their experiences.

"Blokes like me, if they could have been admitted to the army anyway, which would have been a terrible disaster for everyone concerned, would more likely have been kept at home," he says.

"Although there was conscription, that did not mean by any means that everybody went. They chose from the conscripts those that would make the best soldiers to send to Vietnam."

So, says Dapin, he set himself a mission – to fill the gap left by these inconveniently non-literary types who experienced Vietnam.

"I thought I'd just interview them all – I mean, how hard could that be?" he says with a chuckle.

"Unfortunately, I didn't actually know anybody. That was the first problem. I didn't know any Vietnam veterans at all … So what I thought I'd do was interview about 120 National Servicemen."

Eventually, in the process of writing Nashos War, he spoke to 150 men who had gone to Vietnam, and several who hadn't "for administrative or political reasons. But then I just kept on. Even after I finished the book I just kept on doing it. I can't stop".

He has a fantasy, he says, of revising the book and adding more interviews, but he's been told by his publisher that this won't be possible.

So much for his mission to illuminate a gap in the nation's military history. But there's another gap that he managed to identify while writing the book – in his own understanding of the world.

"I never really understood that there were people who thought that to do what you were told was the right thing to do. I didn't get that, I just didn't know," he says.

"I don't know how I didn't know, but I didn't really understand that there are huge sections of the population who believe that it is morally correct to defer to authority. That was kind of huge for me."

And, if he's really honest with himself, he says, he was also on a quest to try and understand his own father a bit better.

"My dad did national service in England when he was a kid. He was in the army. My dad was just an ordinary working class bloke, and after he died, I asked my step-mother, 'Why did he enjoy that, what did he like about being told what to do?'" he says.

"And she said to me, 'Your father didn't know what to do'. His parents died when Dad was very young, and he didn't have any great drive, any great ambition, and there was somebody there who gave him direction, and I guess I found myself talking to a number of people who were like that. I came to a greater understanding I guess of how life must have been for my dad, who died when I was in my mid-20s."

He was also interested in challenging what he sees as a radical misunderstanding of what happened during the Vietnam War, both there and on the home front. But, given that he couldn't keep adding to the stories he collected from National Servicemen, he figured he'd just write a novel set in the same period instead.

R&R is a military police thriller that stems from a story taken from one of his many "Nashos" interviews – that in Vung Tao, a village that served as a logistics supply base, if it rained hard enough, the ground would open up and freshly buried bodies would emerge and float towards the town.

"You'd find them in the street. I didn't really believe this, but I looked it up and I found a memoir of a boat person settled in the US, I think it was, who said the same thing. And I thought it was a really good opening for a piece of fiction," he says.

Peak boring? Not if novels like this have anything to do with it.

Mark Dapin will be speaking about R&R and Nashos War at Muse Canberra on February 7, 3.30pm.