Fiona Farrell feels empty. It's delicious. At Christmas she sent off the final draft of the novel that has been occupying her, almost to the point of obsession, for the past year and more. "The thing about a novel that's wonderful is it's a rich form.

You really can put an enormous amount into a novel, lots of things can be happening all at the same time. So you can read it once for the narrative, but then you can read it again and perhaps get something else out of it. When I'm writing I find myself pouring in absolutely everything I'm thinking about and reading about, and then at the end of it I feel completely wiped out.

Completely emptied." This particular novel sneaked into Farrell's head at the very end of the six months she spent at Donoughmore in Ireland in 2006, after being awarded the prestigious Rathcoola Residency.

The residency, available exclusively to New Zealand or Australian writers and artists, was an extraordinarily fertile time for her. She had gone there expecting to spend the full half-year working on a different novel, Mr Allbone's Ferrets. It was finished in the first six weeks.

Then she wrote The Pop-up Book of Invasions, a collection of poems commenting on the experience of being in Ireland. "I was absolutely blown away by Ireland, I just loved being there. I loved the strangeness of it and the newness of it, so I wrote poems about that." And then, in her last weeks, she went on a four-day car trip through the Burren, a region of County Clare famous for its unusual limestone hills. "Just the most beautiful place. And I started thinking about connections between it and other limestone places that have really moved me, like the ones in France."

That was the genesis of her sixth and latest novel, Limestone. The book follows Clare, a New Zealand art historian, on a quest for her Irish father, who walked out when she was a child and vanished.

The story dives in and out of Clare's childhood, often pausing for extended asides that quietly expand and take over whole chapters: reflections on the horror of being a quiet intellectual trapped next to a boorish rugby fan on a long-haul flight, a hilarious (and all too believeable) account of an academic conference in San Francisco, a lover's relationship-dooming discovery of God on the underside of an avalanche in India. "I wanted the narrative to move forward, and then to pause and reflect.

So it would develop, but not in a single, linear way. I wanted a sense of strangeness and unpredictability - that sense that you're living within the narrative. Not just to tell a simple "and then, and then, and then ..." sort of story."

Each of these diversions has its contribution to make to the larger flow of the narrative, but they also have a stand-alone quality, like little performance pieces or short stories embedded in the book's landscape. The effect is oddly reminiscent of the way strange shapes rise up out of the hills in limestone country. "The way when a child is driving through the landscape she sees caves or horse's heads, things happening, things evolving out of the landscape - that's the sort of thing I was trying to do."

The book is constantly playing with images and ideas built around the unexpectedly rich theme of limestone - a stone composed of the corpses of billions of tiny sea creatures, used by humans for monuments and tombstones, and as the canvas for the very earliest art works.

Limestone, being so malleable in geological terms and yet so hard and unyielding, provides Farrell with a perfect metaphor for the constant changes we experience as we move through the unchanging pattern of human life: birth, growth, age, death, a sequence as solid as stone, but endlessly variable in its details. She works this idea of constant transformation into the book at a very basic level, by telling Clare's story in both the first and the third person, so the point of view we see from changes every chapter, while remaining always the same.

"I like playing with structure, I like working within the novel form and seeing what happens if I rearrange the blocks. In this case, I decided very early on to try shifting from voice to voice, doing third person and first in alternate chapters, and seeing what sorts of things you can say in the third that you can't in the first, and vice versa. Telling the story through two different windows, if you like."

Structural ideas tend to come to Farrell before most other aspects of her novels, and she suspects this is unusual. "It sometimes seems to me that novelists fall mostly into two categories. Some are fundamentally poets, and some are fundamentally journalists. They're either driven by the desire to play with language, or by a more journalistic focus on telling a story."

Whereas she feels a closer connection with the way some artists describe their approach to their work, a physical process of arranging elements in space. "When I've visited an exhibition by someone like Julia Morison, for example, and you move around the gallery and you can see her working around a theme, exploring a theme, trying to make each piece self-explanatory and beautiful, and then moving on and trying a different approach.

Walking about an exhibition like that, I have that feeling of it being a bit like what I'm trying to do when I'm writing." Writing is a very cerebral, introverted process for Farrell. Every morning she goes for an hour's walk from her converted farmhouse on Banks Peninsula, up to the local waterfall and back. "When I'm writing the walk is a kind of reflective time, I'm thinking about what I'm going to do when I get back to my desk. But for the last month or so it's been this wonderful time when I'm just walking along and being aware of feeling physically here again, being back in my body again.

Noticing things. Like at the moment, the paths are absolutely covered with cicada wings and first thing in the morning, they're all glittery. You're walking along and the grass is like sequins or spangles. It's the most beautiful thing."

It sounds a lot like the sort of observation that will turn up in a novel before too long.

* Limestone (Random House, $29.99) is released on April 3.