London (CNN)It all started with a tweet from a concerned big sister.
"Can't believe how awful kids are," Ellis Landreth, 24, wrote on Friday, explaining that her little brother was being bullied for setting up an Instagram account to review his favorite books.
"Kids in his new school have seen it and have created a group chat calling him a creep slagging him off about it and added him to it so he could see," she said, along with a screenshot of her brother Callum Manning's account.
"All I was expecting was a few of my followers to show him some encouragement and support, and that he wasn't 'weird' or 'sad' for preferring to read," Landreth told CNN.
But then the internet did its thing.
A few hours after her tweet, Callum, 13, had raked in thousands of followers.
By Monday, he was Instagram-famous.
"He's absolutely overwhelmed," Landreth said. "He can't even get through all his DMs. He has around 15,000."
At the time of writing, Callum's Instagram account had more than 230,000 followers.
Numerous people replied to Landreth's tweets with their own experiences of being bullied, or to express their own love of books.
A bookstore in Gateshead, near Manning's home in northeast England, even promised him a book on the house.
He also attracted the attention of several authors.
English novelist Matt Haig sent Callum a collection of books, adding: "Hey let's all follow Cals Book Account on Instagram and show him some support."
Authors Caroline Kepnes and Malorie Blackman were among those to share Callum's story on social media.
Callum set up his Instagram account last month, posting his first review of Stephen King's "The Shining" on February 23. "This book was the first book I read in 1 day," he wrote.