Tristan Miller competes in Antarctica in his 51st marathon of 52 in a year in 2010.

Tristan Miller competes in Antarctica in his 51st marathon of 52 in a year in 2010.

FOR most first-time authors in Australia, a $30,000 book advance is something to be grabbed with both hands before the publishers change their mind. But not for Tristan Miller. When Penguin put their offer on the table, he says, ''I'm sitting there going, 'Surely, it's worth 60? You'll sell 100,000 copies, no worries'.''

Miller, 35, admits he was naive, maybe even a bit cocky, but he felt - and still feels - he had a pretty good story to tell. A former advertising salesman, he'd been at a low ebb after his first marriage ended, drinking too much and getting into stupid fights, until a workmate turned him on to running. He was instantly hooked - so much so that he decided to set himself the challenge of running 52 marathons in a year, all around the world.

On New Year's Eve 2009, he set off on his first race, in Zurich. On December 27, 2010, he finished his 52nd, back in Melbourne. Along the way, he had changed his life.

Tristan Miller in action in St Petersburgh, Russia, halfway through his 52 marathons in one year.

Tristan Miller in action in St Petersburg, Russia, halfway through his 52 marathons in one year.

There's a lot of running in Miller's book, as you might expect, but Run Like Crazy frequently reads more like an Aussie backpacker's diary than an athlete's log, with its boozy nights, dodgy tour guides and corny pick-up lines aplenty. ''I actually didn't do it to run,'' Miller says of his epic adventure. ''I did it to go to the festivals, because I wanted to see how exciting the world could be.''

Strange as it may seem to those of us for whom 42.195 kilometres seems an impossible distance to run, a marathon is, in Miller's view, a social experience. ''I'm not a solo runner; I get bored as bat shit,'' he says. ''I love running marathons because I love talking to people.''

He's proud of his achievement, he says as we chat over coffee at his favourite beachside cafe near the home in Middle Park that he shares with Bec, his wife of three weeks (they met through running and cemented their relationship mid-marathon year). But he also knows that in the world of running, it's far from the most outrageous thing anyone has ever pulled off.

Back in the 1980s, a man ran 52 marathons in a year for the first time, all in America. In 2006, a spate of runners had their eyes on the record book: Dane Rauschenberg ran a marathon every weekend in the US, and went back to work each Monday; Dean Karnazes ran 50 marathons in 50 US states in 50 days, sequentially; with far less media coverage, a 26-year-old called Sam Thompson went one better, running 51 marathons in 50 states in 50 days. In 2009, Japanese runner Akinori Kasuda did 52 marathons in 52 days (the first 51 around his local running track, the last the Tokyo marathon). He was 65.

Topping them all is 49-year-old Belgian Stefaan Engels, who in 2010 ran a marathon every day for 365 days straight (he finished in February 2011).

Even for Miller, that's a little too much running. ''I reckon 30 kilometres into every marathon I thought, 'What the hell am I doing here? When is this going to stop?','' he says.

He'd started his peculiar quest because he was trying to answer some of the big questions and because he had started to feel that a career in sales was ''a lot like Groundhog Day; you do the same thing over and over again''.

But, he says, the quest wasn't answering those questions. ''It was just racing. It took me until I was home to put it all into perspective. When you're travelling, you never fully comprehend what's happening to you. It's only when you're sitting on the plane leaving at the end of your trip that you're processing it. But I was already in the next place, ready to go again, so I was never processing it as a whole.''

A couple of months after he returned to Australia, he finally saw the shape of it and that's when he started writing. ''I'd wanted to change the sense of what's possible rather than just chasing more cash,'' he says. ''I did it to change the direction of my life, there's no doubt about that.''

In that he's certainly succeeded. There's the book, there's the marriage, there's a new career as a motivational speaker - he's done half-a-dozen gigs just this month, at $4000 a pop - and there's a plan to tackle the 320-kilometre run through the Alps from Germany to Switzerland in August, with a pipedream to film it as a pilot for a possible TV series.

Closer to home, he has another ambition. He is putting the finishing touches on an 85-kilometre road race from the Yarra Valley to Melbourne to take place next February, an event he hopes will become one of the great races of the world.

''For me, it's the legacy piece,'' he says. ''What if it lasts for 100 years? I'd be so proud. I've based it on what I've learnt from all the races I've run around the world, what works, what doesn't.

''I've learnt a lot and it would be stupid just to let that go, for it to just be something I tell the grandkids. Hell no, I'll feed it into the most epic race in Australia.''

Given his track record, you'd be crazy to doubt him.

Run Like Crazy, RRP $29.95, published by Penguin, is out now.