In 2015, three of the best selling books of the year were adult colouring books. In Canada it was 5 of the top 10 including the top 2.Various people have offered various theories explaining this, but the fact is that nobody anticipated this, certainly not the publishers. This is from an article on the economic uncertainty created by unanticipated innovations. Some innovations are hi tech, but not all of them.
Via Marginal Revolution.