Zoella: how well do you know her? The debut novel, Girl Online, by YouTube blogging sensation Zoe Sugg, otherwise known as Zoella, is expected to top the list of best sellers. It is already at number three on the Amazon Best Sellers chart due to pre-orders alone. If you haven't heard of Zoella, she is one of the most famous and popular of the current crop of YouTube stars, with over 6 million people subscribed to her channel. Her videos feature everything from product reviews to collaborative videos with other YouTubers playing games and practical jokes. Zoella's upbeat, quirky personality - like a favourite big sister - has seen her twice win the Radio Teen Choice Award. She already has her own beauty range. She talks to her fans as if they were her friends and millions feel they know the 24-year-old pretty well. Test how much you really do know about the YouTube favourite, Zoella.