What prompted the sales of colouring books in U.S. to jump from 1 to 12 million units last year? (Nielsen data). How come 5 of the top 10 best-selling books in the United States were adult colouring books in 2015?  And this trend is not limited to just the U.S., it can be seen globally from South America to Asia, with book stores carrying a wide selection of colouring books. In May 2016, Faber-Castell, the world’s biggest wooden pencil manufacturer, said that they are experiencing double digit growth due to the popularity of adult colouring books. In a nutshell, this...