Zoë Sugg (Zoella)’s debut novel Girl Online has become the biggest-selling debut novel ever.

Popular YouTube sensation Zoella has released a YA novel, and it’s selling like crazy. Fans across the world are lining up to buy the 24-year-old’s Girl Online, which has sold over 78,000 copies in its first week.

The book follows the teenage blogger Penny, whose secret relationship with a pop star goes viral. The book is somewhat autobiographical – at least, the blogging part – reflecting Zoella’s experiences with her sensational video blog.

Zoella mainly vlogs about fashion and style, but there’s plenty of personality and fun segments with other YouTube stars. She’s currently got more than 6.6 million subscribers worldwide.

Earlier this year, the English sensation won a Radio 1 Teen Award for best British vlogger.

Following the news, Zoë Sugg writes on her Twitter:

The book has received mixed reviews, with some critics calling it too “sugary,” while her fans are claiming that it has changed their lives.

Of course many outlets are now touting that Girl Online has outsold J.K. Rowling’s debut novel Harry Potter and the Philosopher’s Stone in its first week, but since the latter’s original print run was 500 copies, that’s hardly a fair comparison.

Have you read Zoella’s ‘Girl Online’? What did you think?