Secret Garden: An Inky Treasure Hunt and Coloring Book by Scottish illustrator Johanna Basford made a debut with an initial printing of 13,000 copies.
Total worldwide sales three years and two books later for Basford.
Coloring books for adults as a genre has been around for at least four decades – the assiduously low-cost press Dover Books has been making all these years - but Basford’s success made it a phenomenon.
The number of coloring books of all sorts, sold in 2015 in the U.S, according to industry research firm Nielsen BookScan, up from 1 million in 2014.
of adult colorers are female. While there’s a considerable millennial contingent–36% are ages 18 to 29–boomers enjoy coloring too, with 19% being over 55. Celebrities like Zooey Deschanel and Nigella Lawson are supposedly fans.