As of 5pm yesterday, the office received 198 complaints against the two books, whose titles translate as Internet Strange Tales and Humanity Strange Tales.

The series’ author, Johnny Li, a 24-year-old criminology student at City University, said he and the publisher, Idea Publication, welcomed the rating and would not lodge an appeal.

Li, who goes by the pen name Scary Bird, admitted mishandling distribution, noting the books were displayed on some local bookshops’ bestseller shelves without bearing a warning about their content.

He said the publisher had voluntarily recalled the books from all bookshops for repackaging when controversy broke earlier this month.

Its repackaging efforts included attaching warning notices to the books and wrapping them in plastic.

“What we have done is in line with the requirement of the rating,” Li said.

“We feel the rating is reasonable and welcome the decision. I feel it was the publisher’s and my own negligence at the start,” he added.

Li said he did not want to focus on violence in his books but instead wanted to reveal the dark side of society and of the virtual world.

The books introduce readers to the deep web, a part of the internet not searchable on standard search engines.

The books also contain graphic content, such as a passage detailing the cooking of a little girl.

Psychologists have said that children in general lack self-regulation and are more likely to accept graphic content as normal when they see books are popular among their peers.

The first book has been printed six times, generating about 10,000 copies since its publication in May last year. It was the eighth-best-selling Chinese-language book last year at Taiwan-based book chain Eslite.

There are some 5,000 copies of the second book, which was published earlier this month and has already become the third-best-selling Chinese-language book at Commercial Press.