Zoella: YouTube sensation Zoe Sugg's debut novel expected to become overnight bestseller Though many may not recognise her name, Sugg's book has proved so popular with fans that every bookseller broke the embargo on its sale, according to a spokesperson for the publisher. Girl Online, which is released in the UK today, follows the story of Penny, a teenager who blogs about her hidden feelings on friendship, family, boys and her anxieties. The novel is based in part on Sugg's own experience of charting her everyday thoughts in video blogs or 'vlogs' online. The 24-year-old has become an online sensation after creating video blogs with beauty advice, helping her gain more than 6.5 million YouTube subscribers to her "Zoella" YouTube channel. A video in which her and her boyfriend, fellow YouTuber Alfie Deyes, quiz each other on how well they know one another has been watched more than 6 million times. Her other makeup tutorials and "#AskZoella" videos easily attract over 1.5 million views each. Tom Weldon, chief executive of the book's publisher Penguin Random House, said Girl Online would be sold around the world. Adele Minchin, publicity director at Penguin Random House, said at the book's launch last night: "We're expecting number one this week." Read more: Zoella is not a good role model for teenage girls Zoella is a great role model - she changed my life Zoella is bigger than Beyonce on YouTube