When Penguin Random House announced recently that it had acquired world rights to the next two adult coloring books from Johanna Basford, the so-called queen of coloring, it was just the latest sign that the demand for coloring books in the U.S. is continuing to surge. The first book, Lost Ocean, which contains undersea adventures with Basford’s trademark intricate designs, will be released at the end of October with a 400,000-copy first printing. The second, still-unnamed book will publish in fall 2016.

This isn’t the first coloring book that Penguin Books executive editor Meg Leder, who participates in an occasional lunchtime coloring group with her coworkers, will edit. She’s also published Mel Elliot’s Color Me Swoon, as well as Souris Hong’s Outside the Lines. “I’m really intrigued by the intersection of fine art and coloring. There are a lot of brilliant artists like Johanna, who are inviting users to participate in their art through the act of coloring,” said Leder. She added that she is also drawn to coloring books’ crossover appeal.

Basford’s first book, Secret Garden (2013), which was published by U.K.-based Laurence King and has more than 1.5 million copies in print worldwide, is largely credited with the surge in popularity for adult coloring books in Europe and the U.S.—but the trend really began some months earlier in France, with the publication of Art-thérapie: 100 Coloriages anti-stress in 2012, by Hachette Pratique. The press’s decision to focus on the therapeutic value of coloring paved the way for Basford and a number of other artists. To date,

Hachette Pratique has sold 2.5 million copies of its Art-thérapie series in all formats in France, and another million copies in 18 additional countries.

“When we decided to publish [Art-thérapie], our editorial team studied carefully what could be the main point of coloring when you are an adult,” said Anne le Meur, editorial manager for the Art-thérapie series. The team decided that coloring could help readers attain well-being and meditate, rather than being merely a regressive activity. The binding and overall design also boosted sales. “Because the books themselves are nice, people are collecting them and keep them on their bookshelves,” she noted.

Getting these titles to shelves is one of the biggest challenges facing U.S. publishers, who are having a hard time keeping up with the adult coloring book phenomenon. Although growth was steady over the past year, it’s been explosive this spring, according to Sterling executive v-p Theresa Thompson. Sterling’s bestselling proprietary coloring books—many sold through parent company Barnes & Noble—have sold more than 40,000 copies since 2014, when the press first acquired them. Mille Marotta’s Animal Kingdom, which Sterling offers to all trade accounts, has sold more than one million copies worldwide, more than half of which have sold in the past six months. To keep up with demand, Sterling currently has six different printings of Animal Kingdom in progress with four different printers. It will publish journals and postcards related to the book this summer and add a second book, Tropical World, to the franchise in August.

At Dover, which has published coloring books since the 1970s, the adult coloring category has just begun coming into its own. According to Nielsen BookScan data, Dover’s bestselling coloring book in the January to May 2014 period, on mystical mandalas, sold about 9,600 copies. So far this year, it’s sold 46,200 copies, and four other coloring books for adults have sold 10,000 copies or more. That’s in large measure because of Dover’s Creative

Haven line, which it began shipping in fall 2012. The books are printed with illustrations on only one side of perforated heavy-stock pages, so that the pictures can be framed. Dover now has 120 Creative Haven titles in print and has sold close to 1.8 million copies. “We’ve created $10 million in retail sales,” director of sales Steven Sussman said, adding, “the thing we’re selling the most of now is translation rights. Every day we’re getting new requests.” Dover is also planning to test a range of line extensions for its Color by Number and Paint by Number lines.

The Quarto Publishing Group USA will easily have a million adult coloring books in print this year, with the market continuing to surge, said Ken Fund, president and CEO of Quarto, a publisher of illustrated and creative titles. Those sales are being led by its Zen Coloring Book series, which includes the bestselling Color Me Calm and Color Me Happy, both by art therapist Lacy Mucklow with art by Angela Porter. The books have gone back to press 10 times in the past six months, for a total of more than 275,000 copies worldwide. “We imagined the books would appeal to adults looking to relax. But we never expected the responses we’ve received from people battling serious medical conditions,” added editorial director Jeannine Dillon, who came up with the idea for the series after coloring with her four-year-old son.

Keeping up with bestselling titles has also been a problem at Laurence King, for both Secret Garden and Basford’s second book, Enchanted Forest, which came out in February. “The demand is dizzying,” said Debra Matsumoto, U.S. publicity and marketing manager. “It’s into five digits, in some cases, for one account.” Whenever a new shipment arrives, one or both books climb into the top 10 at Nielsen BookScan and at Amazon. During the months of May and June, Laurence King plans to deliver eight reprints of Secret Garden and four slightly larger ones of Enchanted Forest to the U.S.

The press has been forced to push back the delivery of kits it had created to encourage coloring parties, such as a recent Cocktails and Coloring evening at Face in a Book in El Dorado Hills, Calif. The kits won’t be available until August, so that Laurence King can focus on getting accounts fully stocked. Its newest extension of Enchanted Forest, a postcard book version, will be released this fall.

Given the popularity of adult coloring books, it’s only natural that other companies are trying their hand, too, including Brazos Bookstore, in Houston, which published 500 copies of its second adult coloring book, Hemingwasted, as an exclusive item for Independent Bookstore Day. Little, Brown will release its first four adult coloring books starting in June, all with the subtitle Color Your Way to Calm. The first two are Splendid Cities, by Rosie Goodwin and Alice Chadwick, and Secret Paris, by Zoé de Las Cases. Two other books by de Las Cases, Secret New York and Secret Tokyo, have October pub dates. Like the most successful adult coloring books, all four are printed on high-quality paper, and the Secret Cities books feature “zentangle” patterns meant to lower stress.

HarperOne is focusing on the spiritual nature of coloring. Its newly launched HarperElixir line is introducing a spiritual coloring book series, Coloring Books for the Soul, with mystical illustrations by Lydia Hess. The first two entries, Sacred Nature and Sacred Symbols, are due out in October.

Running Press’s first two adult coloring books also treat coloring as therapy. Each has the copy line “doodle and color your stress away” on the front cover. The books are packaged by Michael O’Mara, who did Running Press’s popular Doodle books for kids, and they feature thick cardboard covers and four-color illustrations inside. Color Therapy and Creative Therapy are due out next month. Editorial director Jennifer Kasius pointed out that the press had only planned to start with two books, but bought a third, showing its confidence that the trend will continue.

Coloring books are certainly selling well at big retailers such as Amazon, where five coloring titles have consistently been among the top 15 bestselling books, including a couple self-published titles from CreateSpace. And they have figured on PW’s own bestsellers, particularly Basford’s books. Publishers also reported selling the books in large numbers in nontraditional outlets.

CORRECTION: An earlier version of this story stated that Sterling's proprietary coloring books are mainly sold through Barnes & Noble and that Animal Kingdom is being printed at publishers around the world.

The Adult Coloring Book Boom

Forests, gardens, mandalas, and animals are popular themes for coloring books aimed at adults. Here’s a sampling of some of the week’s biggest sellers:

Title Author publisher Units
Enchanted Forest Johanna Basford Laurence King 26,345
Detailed Designs and Beautiful Patterns Lilt Kids CreateSpace 5,128
Creative Haven Creative Cats Coloring Book Marjorie Sarnat Dover 4,729
Mystical Mandala Coloring Book Alberta Hutchinson Dover 3,653
Flower Designs Coloring Book Jenean Morrison Test Pattern 3,485
Creative Coloring Inspirations Valentina Harper Design Originals 2,764
Creative Haven Art Nouveau Animal Designs Coloring Book Marty Noble Dover 2,402
Enchanting English Garden H.R. Wallace H.R. Wallace 1,614
Coloring for Grown-Ups Ryan Hunter Plume 1,403
Creative Coloring Animals Valentina Harper Fox Chapel 1,292