Despite the fact she has a new book out and a skin-care line on the shelves in April, she is focused on a big life-changer of an event due to occur in late May.

"We feel very fortunate to have fallen pregnant," she says. "We're actually beside ourselves. Hamish particularly is very excited - he's wanted to be a dad since before he was born. And I'm extremely excited and looking forward to a whole new focus."

The pair were firm friends when they collaborated on a book in 2009, aptly called Textbook Romance and subtitled How to find the guy, make him fall wildly in love with you and keep it that way.

Foster Blake must have followed her own advice: they soon began dating and were married in secret on December 11, 2012, Blake's 31st birthday. And now the baby.

For a relationship that's been somewhat played out in the press, on radio during Blake's popular Hamish and Andy program, even through their matching columns in a News Limited magazine, listening to Foster Blake talk about her husband and how they're coping with the idea of a baby still seems a little intrusive.

"I've had incredible support from my husband and his family and my family and friends who have been down this path," she says. ''But I realise you can read all the literature and think you're prepared but you can't really be prepared until the baby arrives.''

They've deliberately not found out the sex of the baby - "we like surprises" - and have their Melbourne nest in order and are looking forward to a little down time for the next few months to prepare for the birth.

"It's a whole new kettle of fish for us, trying to get everything done before then," she says.

So let's get the publicity for the book out of the way. The Wrong Girl is Foster Blake's fourth novel. As well as Textbook Romance, she's also written Amazing Face, a how-to guide on beauty and make-up. The Wrong Girl is another story firmly set in the chick lit genre. Thirty-something woman with relationship and career doubts, a bit of sex, a lot of humour, nothing that will make you think too hard, just a good rollicking read.

"It's by no means a serious novel. I've never been a serious writer so why start now," she laughs. But she has a knack for character and situation and selling books.

While her previous novel The Younger Man touched on marriage and babies, she made a deliberate choice with The Wrong Girl to set the story firmly in singledom.

"I actively and consciously pulled back from marriage and babies with this one. While I want my readers to grow with me, I didn't feel as though I had completely finished in that single girl arena yet. I still very much enjoy playing there.

"I'm sure once I've had a baby, whether I want it to or not it, the next stage of my life will infiltrate my work.

"But for now I've still got plenty of single girlfriends, doing the Agony Aunt column for Cosmo, I'm still hearing plenty of angst and questions from women in their 20s and 30, questions about relationships and careers and life choices."

She describes The Wrong Girl as something of a coming-of-age story.

"While there's still a romantic narrative, there's a big focus on Lily's career and it's about her growth and development in that area too."

Foster Blake grew up in the Southern Highlands, one of six children of the novelist David Foster. She studied media and communications at the University of NSW, worked in magazines, including a three-year stint as beauty and lifestyle director for Cosmopolitan.

She was quick to embrace the online world, developing beauty blogs fruitybeauty.com.au and primped.com.au and as a contributing editor at Mamamia.com.au.

Now she has more than 36,000 followers on Twitter (Foster Blake and Blake announced both their engagement and wedding via Twitter - what are the odds we'll first hear of the baby this way?) and a website at zoefoster.com.au.

Her first novel Air Kisses was published in 2008 and as well as writing her books she helped create an app for Amazing Face.

"I'm at my most productive when I'm busy," she says. "If there's a void I fill it with nothing and waste too much time on the internet and watching bad television. When I'm super busy I'm at my most powerful."

Foster Blake says her secret is not taking herself too seriously, admitting that women of a certain age, trying to build careers and relationships, can fall into that trap too easily.

"Not taking myself seriously has always been my mantra. Everything is allowed to be fun. Humour is very much the framework by which I live my life, in terms of how I write, my blog, with my husband.

"So much of our life is spent laughing and having fun. We think it's a pretty lucky way to live life. We feel very blessed in that sense and I feel sad for people that don't get to engage in that aspect of life as much as we do."

She says having the baby will be like having another kid in the house.

"That's the most exciting part for us, that we'll have this funny little person making us laugh."

The Wrong Girl by Zoe Foster is published by Michael Joseph, $29.99.