JK Rowling has thanked fans of Harry Potter for making her books a success, exactly 20 years since the first volume was published.

Harry Potter And The Philosopher’s Stone was first published on June 26, 1997, and has since sold more than 450 million copies worldwide in 79 languages.

Rowling, who wrote the first book in a small cafe in Edinburgh, posted on Twitter: “Twenty years ago today a world that I had lived in alone was suddenly open to others. It’s been wonderful. Thank you.”

The National Library of Scotland held a one-day pop-up exhibition to celebrate anniversary, the centrepiece of which was a rare first edition of the book containing personal notes and drawings by Rowling. In it she says that the book “changed [her] life forever.”

An exhibition celebrating the magic of Harry Potter will open at the British Library in London on October 20.