GIRL Online, the debut novel by the beauty blogger and vlogger Zoe Sugg, is 2014’s fastest-selling book.

It shot straight to the top of the UK Official Top 50, shifting 78,000 copies in seven days and outstripping first week sales of even JK Rowling.

How did the newbie novelist manage that? Largely thanks to the legion of fans who follow her Zoella YouTube channel.

With nearly seven million subscribers, that means less than 2 per cent have bought the book so far. And with plenty of Christmas wish lists still to be fulfilled, you can bet sales will continue to soar.

No doubt to her publishers’ delight, Sugg has managed to leverage her internet fame to boost physical book sales.

Meanwhile, an established British author is looking to harness YouTube in a similar way.

The Night School Web Series is a six-part video spin-off of CJ Daugherty’s bestselling YA books. Each of the sub-10-minute episodes features an original story but uses the same cast and setting as the Night School novels.

“I am barraged with emails and messages every single day from fans asking for a TV series or film of Night School,” says Daugherty. “This was a way to give them what they want and to be at the cutting edge of something brand new.”

Night School’s online offering is a UK first, but over in the US, these literary offshoots are nothing new. There’s a whole subgenre of classic lit reimagined for the Facebook generation, like The Autobiography Of Jane Eyre and the Lizzie Bennet Diaries, based on Pride And Prejudice, which started out on YouTube before spawning a book.

With millions of video views, not to mention millions of pounds spent on books and merchandise, clearly the multi-platform approach is a lucrative one. It’s not without controversy though.

Both Sugg and her ghostwriter, Siobhan Curham, were forced to defend themselves when they faced online abuse and accusations that Sugg hadn’t been transparent about how much help she had in writing Girl Online.

Sugg eventually announced she was “taking a few days out and off the internet because it’s clouding up my brain”. So will the vlogger-turned-author’s experience deter other YouTubers from launching their own literary careers? One look at her record-breaking sales suggests not.