Crown Princess Mette-Marit of Norway to open Norwegian erotica exhibition

She describes herself as a "dedicated bookworm," so it doesn't come as a great surprise to learn that Princess Mette-Marit of Norway is set to open an exhibition at the National Library in Oslo on September 24. But what is a surprise is the subject matter of the exhibition – erotica.

The National Library in Oslo said they "greatly appreciate" bookworm Princess Mette-Marit opening the exhibition Photo: Getty Images

'The Red Ruby — Erotic Transgression In Norwegian Literature' takes its title from a novel by Agnar Mykle.

The Song of the Red Ruby, which was released in 1956, is set just before World War II and features detailed descriptions of sex. It caused an outcry in Nowway and the author and publisher were subsequently tried for obscenity and the book was pulled from shelves. After a long legal battle, which included a trial and appeal, the Supreme Court of Norway declared that the book was not obscene.

The Royal House of Norway has confirmed that the Princess will attend. "We greatly appreciate Princess Mette-Marit opening this exhibition," which celebrates Mykle's 100th birthday, said Aslak Sira Myhre, the National Library's director.

Mette-Marit is an advocate for literacy and for the past two years has transformed her royal train carriage into a rolling library that has traveled across Norway. At each stop the princess met with locals to encourage a love of reading as well as talking to authors.

The mother of three, who has said in the past that she"cannot imagine a life without books," admitted to local newspaper Dagbladet that she'd read some more recent erotic literature – 50 Shades of Grey.

"I have read some pages of it," she laughed before saying that the benefit of getting older is that she doesn't need to spend time reading things she doesn't like. "It's so amazing, being able to put down a bad book!"

The princess has denied that she plans to write a book but joked in May that maybe her daughter, Princess Ingrid Alexandra, 11, will be an author.

"When she was little, before she had learned to write, she would trick people into writing down the stories she dictated to them," she told the audience at a literature festival in Lillehammer.