One of the authors whose books have disappeared off the shelves of the SAR's public libraries in recent days says this represents the new normal for the city and will intensify.
Web searches for a number of titles written by authors such as former Demosisto leader Joshua Wong, Civic Party lawmaker Tanya Chan and prominent localist Chin Wan show that the publications are no longer available and are 'under review.'
The Leisure and Cultural Services Department says it's checking books to see if they comply with the new national security law, but didn't name the books.
One of the writers, Chin Wan, who says Hong Kong should become an autonomous city state, told the BBC on Saturday that this was "a sad thing because censorship is quite unusual in Hong Kong - unless for some obviously sexual things - but not this kind of political writing".
Asked if he thought this was the new reality for the SAR in the wake of the new national security law, Chin said it was.
"I think so. They're coming, and they're coming more and more obviously - after freedom of speech, after books, after posters being posted in restaurants as well as in the streets and flags saying that Hong Kong should be free - or even wearing a T-shirt that simply says 'Free Hong Kong'.
Chin said he thought they should be available in bookshops but anticipated difficulty getting books printed in the SAR, but added that he might have to print in Taiwan.
He said he was not worried about his own safety yet.
"But I think they will come after me. They will increase the pressure bit by bit by testing the reaction of Hong Kong people as well as the international world," Chin said.
Joshua Wong's books detailing his role in mass protests against national education in 2012; and the 2014 Occupy Movement have also disappeared from the shelves, and Wong called it a form of 'white terror.'
In a social media post, Wong said his books have nothing to do with sovereignty and were written before he got involved in international advocacy work. He said the security law was just a tool to penalise speech crimes in Hong Kong.
Tanya Chan's book about protests has also been pulled off the shelves, although her titles on less sensitive issues like drama are still available.