Graeme Simsion shares The Talk he gives new fathers while toying with third Rosie book idea

He's enjoyed breakout success, counts Bill Gates as a fan and has taken to writing full-time. But among his friends, author Graeme Simsion is known for The Talk, and it's what he does to help fathers ensure their relationship stays together during the stress of a newborn.

Melbourne-based Simsion became a worldwide hit with his debut The Rosie Project, the tale of an eccentric man in want of a wife.

The book and its sequel, The Rosie Effect, have sat at the top of worldwide bestseller lists for months, with the screen rights optioned to Sony Pictures Entertainment back in April.

Last week audiobook publisher Audible.com.au made the first book available free from its subscription website, with the title and its sequel being read by Australian actor Dan O'Grady.

But as New Zealand-born Simsion toys with ideas for book three - an uncontracted fourth novel is still on the drawing board - he shares the little- known secret of what prompted him to write a second Rosie novel.

"It was unexpected for me. I had absolutely decided I was not going to write a sequel," he says.

"I am a believer that romantic comedies in general shouldn't have sequels, we finish with the little conceit that everybody lives happily ever after and we don't venture into that territory that those of us who have been in relationships know, which is of course that life continues challenging."

Simsion's first Rosie novel ends with a love match between order-loving Don Tillman and his matchmaker and theoretically unsuitable mate Rosie Jarman. The second tale begins with the couple in New York finding they are about to become parents, kicking off a saga that will upturn their lives.

Simsion explains just what prompted him to return to the couple's adventures.

"I went out to dinner with my writers' group and we were celebrating a pregnancy of one them and one of the others said 'Graeme, you've got to give Mark' - who is the expectant father - 'The Talk'. I have this talk I give to men who are about to become fathers for the first time and it struck me that Don Tillman needed to hear The Talk," he says.

"It all went from there. I realised that pregnancy would throw a challenge at Don and there was still some life in the man if we threw some challenges at him and that would be a way of throwing the challenges of a relationship in general, and indeed of being in the world, at Don and seeing how he responded - so I got into it with some enthusiasm."

Simsion has been married for 25 years to Anne Buist, a psychiatrist and women's mental-health chairwoman who will her own debut novel early next year. The father of two gives the lowdown on exactly what constitutes The Talk.

"I say to men that while their partner is occupied with the child, particularly in the very early months, they need to take personal responsibility for the continuation of the relationship," he says.

Don is certainly in need of good advice in The Rosie Effect, as he gets into a world of trouble behind Rosie's back, with his highlights including a suspicious "incident" in a playground, a run-in with his building supervisor and an enforced stint in therapy. His dodgy sidekick David Borenstein comes along for the ride but ultimately it's up to Don to get past Rosie's newly built defences after his train-wreck behaviour.

Simsion is contracted to produce a third book - but not a Rosie novel. He says there are still messages he could get out to parents with the series.

"I think that the obvious prompt for the third book is if we were to go down five or six years, or seven years down the track and imagine a child - still at that age that parents can still make a very big difference and perhaps turning out a little like Don - and raise questions about how much parents should choose to influence their child."

With The Rosie Project film production already at the director stage and The Rosie Effect about to hit US shelves on December 30, the ball is definitely in Simsion's court.

"Let's hope he chooses to return serve and continue influencing his own child, Don.