Coloring books for grownups are topping national best-seller charts on the Amazon and Barnes & Noble websites.

“They’re extremely popular,” said Laura Skinner of Lake Forest Book Store, which carries 10 different versions of adult coloring books.

According to The Daily North Shore "Owen Keenhen of The Book Stall said store had a hard time getting the coloring books in stock due to high national demand. The store now carries two different adult coloring books for customers."

Secret Garden: An Inky Treasure Hunt and Coloring Book and Enchanted Forest: An Inky Treasure Hunt and Coloring Book, both by Joanna Basford, are best sellers at both stores. Each 100-page book retails for $15.95.

“I think adults have really come to see them as a great stress release, a great way to pass some time,” Skinner said. “We had a customer in yesterday whose neurologist recommended [adult coloring books].”

Skinner said Lake Forest Book Store began carrying coloring books for grownups when they first came out in spring 2013.

“They just flew off the shelves,” Skinner said. “Secret Garden went to backorder. Now it’s gone again.”Skinner said she noticed a big rise in popularity after an article in the New York Times discussing the new trend.

Keenhen said he believed customers buy the coloring books as gifts as well as for themselves. “It’s a nice activity to do while watching TV,” Keenhen said. “I think its therapeutic and calming for a lot of people.

Keenhen said The Book Stall sold about half a dozen adult coloring books in the last two weeks. He said these numbers represent healthy sales, but not an all-out craze.

According to the New York Times article from March 2015, Basford’s coloring books have been a hit abroad as well as in the United States, with especially high sales in South Korea. The Times reported Basford’s first book Secret Garden had sold 1.4 million copies in 22 languages since its release.

Basford, who illustrated each of the elaborate black-and-white ink drawings of leaves, flowers, birds and trees that fill her book, told the Times she initially had doubts of whether or not people would be interested in an adult coloring book. A fan of Basford’s work told the Times she attributes the book’s popularity to its ability to “transport you back to a gentler time of life.”

Basford’s success has motivated many leading publishers to seize onto the trend. In addition to Basford’s popular titles, Adult Coloring Book: Stress Relieving Patterns by Adult Coloring Book Artists and Balance by Angie Grace hold spots on the Amazon best-seller list.