For the first time since the Hong Kong book fair began in 1990, veteran publisher Jimmy Pang will not display any political books at his booth.
The book fair, which draws about 1 million visitors each year, was canceled last year due to the global health crisis.
It resumes this week under the shadow of a new national security law.
Authorities have warned against quote "subversive" or "separatist" books, two vaguely defined crimes.
"For so many years, from the first book fair that I have participated in until now, this year's book fair is the most perilous one. In the past, we have no such worries, but this time our self-censorship is so serious."
Pang would have liked to display a book that documents Hong Kong's youngest protesters and "A Sea of People" by Claudia Mo, a former legislator who was arrested under the new law and denied bail.
But he decided against it, and said he wanted to quote "avoid trouble."
Another publisher Raymond Yeung said editors were instructed to follow certain "red line or regulations."
In one of his new books, he blurred out the logo of Hong Kong newspaper Apple Daily in an illustration.
The pro-democracy tabloid printed its last edition in June after police froze its assets and arrested its executives in a national security probe.
"Actually, there are other three books that we want to display here but they are banned by the printers already. So they have already done some kind of censorship for us. Like they feel that actually the content may not be safe, that they do not want to take risks because of the Apple Daily incident."
The government's Trade Development Council, the organizer of the fair, said books would not go through a vetting or censorship process.
But exhibitors had to be quote "self-disciplined."