[Photos of the Tiananmen protests from a student witness.]

For years, Hong Kong publishers found a ready audience of mainland Chinese readers who wanted books they could not find at home and could sneak back into mainland China. But the industry has declined thanks to tighter border checks, the consolidation of Hong Kong distributors and retail outlets under mainland control, and the disappearance and imprisonment of independent booksellers.

“Authors are afraid to publish. Publishers are afraid to continue doing business. Distributors are also afraid,” said Yaqiu Wang, a China researcher for Human Rights Watch. “Bookstores are diminishing and people there are afraid, too. So are the buyers, of course. It’s an attack on the publishing industry from all aspects.”

New Century Press last week released “The Last Secret: The Final Documents From the June Fourth Crackdown,” a collection of statements and speeches on the Communist Party’s decision-making process in 1989, as well as an analysis of top leader Deng Xiaoping by the veteran journalist Dai Qing, and a memoir by the academic and Tiananmen hunger striker Zhou Duo. The three new books are particularly important to Mr. Bao. Now 52, he was a college senior in Beijing in 1989, and his father was the most senior Communist Party official to go to prison for siding with the calls for political reform.

“I met a lot of people at Tiananmen,” Mr. Bao said. “The event really changed our lives. It certainly changed mine.”