Author Craig Smith perches on a stool, pushes his long hair back and gets his guitar in place to sing the first lines of his new book – already a bestseller – and glances across the Herald's studio to the little girl who helped inspire it.

The new book is The Dinky Donkey, a follow-up to Smith's wildly successful The Wonky Donkey, and the little girl is his bright-as-a-button daughter Maia, 4.

"That's me!" she says, pointing to the cover of the book illustrated by UK-based artist Katz Cowley where a dinky donkey, with long eyelashes and pink-painted hooves, takes pride of place. She's also a donkey who likes loud music – something Maia has a penchant for – and she clearly adores her dad.

Introductions done, Maia turns her attention to the ruru (morepork) soft toy she is clutching (in hands with rainbow-painted nails). It's been a big couple of days for the pre-schooler and her dad who are in Auckland to launch The Dinky Donkey.

They've visited a school (West Harbour, near Massey), been on television and met the woman who changed Smith's life forever when, giggling all the way through, a video of her reading The Wonky Donkey went viral.

Scottish grandmother Janice Clark, flown from Australia for The Dinky Donkey launch, helped sales of the first book shoot from 750,000 since its 2009 release to more than two million. Earlier this year, Smith told the Herald on Sunday he watched in disbelief as the book became – at least for a couple of weeks - the number one bestselling book, across all genres, in the world.

The Dinky Donkey has already clocked up pre-orders in the UK of around 50,000 and, in the United States, 60,000, while it debuted at No 1 in the New Zealand bestseller lists.

"The first print run of The Wonky Donkey was 3000; the initial print run for this book is 500,000 so it's pretty surreal," says Smith, whose eyes light up when he looks at Maia.

"Sometimes it takes a while to register because I am so focused on stuff that's going on immediately around me."

Like potentially missing a flight from his Queenstown home to Auckland because of cancellations.

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"But Air New Zealand was wonderful – they helped sort everything out… Sometimes, I am just so busy that it can be days or weeks, even months, before I get to take a break and it really registers."

Smith had wanted to write The Dinky Donkey since before Maia was born or Clark propelled The Wonky Donkey to worldwide fame.

"I had a lot of adjectives left over and knew I could do something with them."

The original story was inspired by a joke Smith overheard at the Te Anau Rugby Club – "what do you call a three-legged donkey?" – and its follow-up, although it had been in the planning for some years, was strongly helped by Maia.

Now, he might produce a third book – making the Donkey series a trilogy – about the Dinky Donkey's grandmother. After all, says Smith, he owes the "grandmothers" in his life a debt of thanks.

Craig Smith's latest children's book The Dinky Donkey is out now. Photo / Michael Craig

It was his own mother and Maia's grandma, Maureen Thomson, who helped him create the story for his first book Willbee – the Bumblebee and Friends, which was published after The Wonky Donkey. In a nod toward Janice Clark, the words may have a slight Gaelic ring to them.

"I usually come up with a concept first and sometimes more comes from just sitting down and jamming. I always write the music to the lyrics and not the other way round."