China's book retail sales boomed in 2013, with online sales exceeding 16 billion yuan (2.56 billion U.S. dollars), a 30 percent year-on-year increase, according to a report published by the People's Daily on Thursday. The report was jointly issued by China Central Television, the People's Daily, book-selling websites, and Horizon Research Constancy Group. According to figures provided by baidu.com, China's largest Web search company, people between the ages of 20 and 39 search for books on the search engine more than any other age group. Men mainly search for books on the arts, textbooks, science and literature, while women search for social science books the most. In the last three years, Chinese people continued to increase their reading on mobile devices. Online retailer jd.com said that mobile device users read e-books for 30 minutes five times per day on average, and they mostly read at home or on the subway.