Second-hand bookshop is a treasure trove.[Photo provided to China Daily]

Duo Zhua Yu was founded in January 2017 and had soon won a large following of people like Shen, buying and selling their books to it and helping to turn the online market for secondhand books into a very prosperous one.

During the recent Singles Day online shopping spree, when tens of thousands of sellers cut prices to attract customers, Duo Zhua Yu said it would pay more for the books it bought for 24 hours and in doing so its inventory swelled with the addition of 100,000 books, which it says is five times the number of books it usually buys each day.

Wei Ying, 32, founder of Duo Zhua Yu and a former employee of the e-commerce company Alibaba, says the idea of opening an online secondhand bookstore arose from her experience selling old books and CDs when she was a university student in Beijing.

At the time she was addicted to reading books and watching movies, she says, but soon realized she could not possibly afford all the books and CDs she was keen on, so she began to sell her old ones to buy new ones.

Wei set up a stall on the campus of the Communication University of China, selling her wares a little below the original price. She sold some popular CDs at the original purchase price, she says, giving her a sense of achievement.