Illustration: Chen Xia/GT

We all know that the book industry is in crisis, but it is sad to hear that some publishers are trying to lure readers by advertising their books as "inappropriate for children."

A book entitled Chinese Lovers, published by Jiangsu People's Publishing Ltd this March, for example, says on its cover right above the book title that "readers under 18 years old should read with caution," with an exclamation mark at the end.

While the naïve might see it as a kind warning, those with a minimum understanding of China's book industry will know that the phrase is no different from a declaration that says: "This book features adult content, and people who understand this underlying meaning should check this out."

This is because there is no book rating system in China that makes it illegal or improper for bookstores to sell books that are "inappropriate for children." As long as a book is published, it means the book has bypassed some kind of content control and anyone has the right to buy it, leaving such a warning basically useless.

In Taiwan, books rated as "restricted" are sold separately and it is illegal for bookstores to sell them to underage children.

In the US, films are rated as NC-17, which means "no one 17 and under admitted," with a price: their box office performance often suffers as a result because mainstream theaters sometimes refuse to screen a movie knowing they will lose revenue from a key audience demographic.

But in China, according to the Youth Daily, shop assistants at bookstores said that some teenagers showed a particular interest in such books, but the bookstores have no right nor any obligation to stop them from buying or reading them.

Can publishers provide content warning to readers? Of course they can, and some of them probably do so out of goodwill. However, until a book rating system is established in China, such warnings are misleading and even tempting for rebellious teenagers. I therefore think regulators of the book industry should ban such warnings for now.

Interestingly, unlike movie rating systems which are common in Western countries, book rating systems are rare or are considered controversial in developed countries.

This is partly due to a belief that since books are not a visual medium, graphic scenes depicted in books do not have as strong an impact as those depicted in films, comics or video games.

Also, in the US in particular, slapping age ratings on books is a non-starter. According to U.S. News & World Report, Beth Yoke, executive director of the Young Adult Library Services Association, an offshoot of the American Library Association (ALA), said that "ALA's interpretation on any rating system for books is that it's censorship."