IT has been the “hardest secret” that Australian children’s book author Mem Fox has had to keep for a year.

Now her famous book Possum Magic “has the magic to turn into money”, which she finds “fantastically weird”.

Illustrations from Fox’s best-known picture book will appear on three limited edition $2 coins, which will be distributed through Woolworths supermarkets across Australia.

Each coin carries illustrations that were first done by Possum Magic illustrator Julie Vivas.

Fox, 71, said she and Vivas had to approve each coin, which has been produced by the Royal Australian Mint.

The coins carry a different illustration of Hush, the main character in the book.

“In the last year we’ve had thousands of emails about the coins and my head is nearly blown off with excitement about this,” she told News Corp Australia.

“They all look like heaven.”

Fox said Possum Magic is so “special” to her that she would never write a sequel to it, or turn it into a series.

“I tried once three years after it was born, but it’s so special and it’s unique, there’s nothing else like it,” she said.

“It would have wrecked it, I did try, but it was pathetic. I would have killed it, I slapped myself and didn’t do it.”

Fox said she still pinches herself when she thinks about the success of the book, which has been read by children all over the world for 34 years.

“When I went to Oman and read it to kids there that don’t know the story, they’re just alive with it, they’re on the edge of their bottoms,” she said.

Fox added that most people don’t realise that Possum Magic was also written “out of anger”.

“I found it very difficult to find a very Australian book for my daughter when she was growing up, I thought this is ridiculous,” she said.

“There’s not a moment of fury in it.”

Fox’s latest book I’m Australian Too!, which celebrates Australia’s cultural heritage, was also written while she was in “such a rage” about our country’s current political landscape.

“The Australian character is a warm-hearted open, genuine, friendly and accepting,” she said.

“Both sides of politics have been led by nasty voices. We welcome strangers even though we don’t seem to be doing at the moment.”

Fox made headlines earlier this year after she was detained at Los Angeles Airport with immigration officials.

While she has been to America 117 times, she told News Corp that she now feels “reluctant to go back”.

“I have never received so much hand written mail from Americans saying ‘This is not our country’, ‘This is not who we are’, ‘I’m so sorry it happened to you please come back.’”

The first Possum Magic $2 coin is released at Woolworths today, with the second design released on Tuesday August 22, and the third will be available from Tuesday August 29. There will be two million pieces of each coin circulated across the country.

The Royal Australian Mint is also releasing a limited edition Possum Magic Coin Collection that will be available at Woolworths and the Mint.

The album features all three $2 coin designs, four different $1 coin designs and a unique 1 cent coin.