Censorship was there in mainland China but books were still easy to carry around and read.
From the wikia: "Despite Jinyong's popularity, some of his novels were banned outside Hong Kong due to political reasons. A number of them were outlawed in the People's Republic of China in the 1970s as they were thought to be satires of Mao Zedong and the Cultural Revolution; others were banned in the Republic of China on Taiwan as they were thought to be in support of the Communist Party of China. None of these bans exists today, and Jinyong's complete collection has been published multiple times in Hong Kong, Taiwan, and Mainland China. Many politicians on both sides of the Straits are known to be readers of his works; Deng Xiaoping, for example, was himself an avowed fan."