An unauthorised book recording TikTok owner Zhang Yiming’s social media posts between 2010 and 2016 has become popular online as Chinese netizens rush to get a glimpse of the young tech billionaire’s thinking at a time when he is maintaining a low profile. Zhang, 38, is one of the most successful entrepreneurs in China after turning a start-up that began life in his small residential flat into global social media giant ByteDance within a decade. However, amid Beijing’s broad regulatory crackdown on Big Tech companies, Zhang stepped down from his role as chief executive in May to focus on “longer-term…