Harry Potter author J.K. Rowling is set to make her screenwriting debut with a film series based on a Hogwarts textbook from the boy wizard franchise.

Fantastic Beasts and Where to Find Them will be the first release in the spin-off movies and "is neither a prequel nor a sequel to the Harry Potter series, but an extension of the wizarding world".

In a post on her Facebook.com page, she adds, "It all started when Warner Bros. (studio bosses) came to me with the suggestion of turning Fantastic Beasts and Where to Find Them into a film. I thought it was a fun idea...

"As I considered Warners' proposal, an idea took shape that I couldn't dislodge. That is how I ended up pitching my own idea for a film to Warner Bros.

"The laws and customs of the hidden magical society will be familiar to anyone who has read the Harry Potter books or seen the films, but Newt's (the author of the fictional textbook) story will start in New York, seventy years before Harry's gets underway."

The Potter books spawned a total of eight movies, starring Daniel Radcliffe as the young wizard, and raked in $7.7 billion worldwide, making it the highest-grossing film series of all time.