King Frederik has revealed a gushing tribute to his Australian-born wife in a surprise book, published just days after he ascended to the Danish throne.

The Danish royal family announced the book’s publication on its Instagram channel on Wednesday.

The posting included a quote from the book: “I am the person I am. I will endeavour to show that as King of Denmark too.”

The book is titled Kongeord. Literally translated, that means The King’s Word. But it can also be seen as a reference to the motto he stated for the first time from the balcony of Christiansborg Palace after he ascended to the throne on Sunday: “United, committed, for the Kingdom of Denmark.”

Publisher Politikens Forlag said King Frederik discussed the ideas behind his motto in the book.

Also among its 110 pages is a passage paying tribute to Frederik’s wife, Hobart-born Queen Mary, and their four children. It also hints at the affair scandal that rocked the Danish monarchy last year.

“I love marriage, my wife, our children and the whole happy base that arises for the people who manage to stay together and persevere,” the King wrote.

The scandal broke in October, when then-Prince Frederik was snapped on a “private” trip to the Spanish capital Madrid, with unsubstantiated allegations he linked up with Mexican socialite Genoveva Casanova while there.

He spent hours with Casanova, including dinner at a busy restaurant in the heart of Madrid. Paparazzi photographed the royal leaving Casanova’s apartment early the next morning.

Casanova emphatically denied any suggestion of a “romantic relationship” and threatened to sue. The Danish royal palaces refused any official comment.

The scandal was apparently overtaken when Frederik’s mother, Queen Margrethe II, made her bombshell New Year’s Eve announcement of abdication after 52 years on the throne.

He became King on January 14, with Mary by his side as the country’s new Queen. The couple were cheered on by thousands of well-wishers in the square below Copenhagen’s Christiansborg Castle balcony after the announcement became official.

Then, on Thursday (Australian time), came the book. Its publication just days after Frederik’s ascension was a surprise, but it is proving popular.

The BBC reports The King’s Word is selling about 25 copies a minute – at 250 Krone ($55) each. It will likely be the Scandinavian nation’s biggest seller in years.

In a Facebook post, the publishers said the book was also about the history of Denmark and the life of the King “from young, reluctant crown prince to mature man, family man and monarch”.

In the book, Frederik admits to struggling emotionally as a child with the knowledge he would one day be King of Denmark.

“I just wanted to be like all other boys of my age,” he wrote.

His thoughts were recorded by author Jens Andersen, who previously wrote Frederik’s 2017 biography. The book is based on 18 months of interviews.

-with AAP