"Girl Online" is a young adult novel written by Zoe Sugg, also known as Zoella. The story follows a teenage girl named Penny Porter, who navigates the challenges of high school, friendships, and first love while managing her anonymous blog about her life. As Penny's online presence grows, she faces the pressures of fame and the complications that come with it. The novel explores themes of identity, mental health, and the impact of social media on personal relationships, making it relatable to many young readers today.