Enchanted Forest by Scottish illustrator Johanna Basford is published in Chinese.[Photo provided to China Daily]

Coloring books once thought to belong only to children are now being used by adults, at least to release stress and for showcasing on social media.

After becoming popular in some Western countries as a recreational activity for adults and children alike, the coloring book is headed toward the Chinese market in the hope that the publishing industry here will make room for it.

A case in point is Secret Garden: An Inky Treasure Hunt and Coloring Book by Scottish illustrator Johanna Basford. It has been popular among Chinese readers on all major online bookstores, including Amazon, JD and Dangdang, since a Chinese version of the book came out in June.

"We have noticed that coloring books were gaining popularity in the United Kingdom, France and the United States since last year," says Fu Zhihong, marketing editor of Post Wave Publishing Consulting. The Chinese company imported Basford's Secret Garden and is set to publish the Chinese version of its sequel, Enchanted Forest: An Inky Quest and Coloring Book, on Friday.

About 2 million copies of Secret Garden have been sold globally since it was first published in 2013.

Coloring books for adults usually come as collections of black-and white drawings, inviting readers to fill in their own colors. In Secret Garden, for instance, there are many drawings of flora and fauna with creatures hidden in the intricate designs.

"It has become a trend worldwide, and many Chinese publishers bought the copyrights of such books from Western publishers," Fu says.

A South Korean TV drama called The Producers made the Secret Garden book popular in China.