Sales of Kiwi Wonky Donkey book spike after grandma's viral video

Sales of a Kiwi classic children's book have skyrocketed after a video of a Scottish grandmother reading it to her grandson went viral.

Scottish grandmother Janice Clark couldn't contain her laughter when she read The Wonky Donkey book to her four-month-old grandson Archer.

"Well I had been reading the little fella books and that and my two daughters say 'hey mum have a read of this one' and I have never read The Wonky Donkey before, and they were sitting giggling in the corner and unbeknown to me one of them was videoing." she told Newshub.

"Next thing I see it on Facebook and I think 'oh what have they done.'"

The well-known book about adds in a new adjective every few pages to the end of the sentence - the final sentence in the book being "spunky, hanky-panky, cranky, stinky, dinky, lanky, honky-tonky, winky, wonky donkey."

Ms Clark finds the sentences hilarious and cannot contain her laughter while reading the book.

"I lost it, I lost the plot and got a bit of the giggles and that was it," she said.

"I'm glad I've managed to brighten up a lot of people's days."

The video of Ms Clark has gone viral gaining millions of views on Facebook and Youtube.

The book's Kiwi author Craig Smith told Newshub the spike caught him by surprise and prompted him to order an extra 45,000 copies of the book because it has sold out in the US and the UK.

"It's a best seller already, now the world's just getting to find out about it [the book].

"She's amazing, Janice and her family."

"And the Scottish accent - everything is funny in the Scottish accent but she has a laugh with it too."

Mr Smith says he has spoke to Ms Clark and her family to thank her for the video.

Newshub.