I am in London at the moment and an seeing even more adult colouring magazines and books than when I was in the UK a month ago.
This photo shows the range I saw near the counter of a WH Smith store on Oxford Street today. Deeper into the business they had a large range of adult colouring magazines in their magazine department. Even more interesting, none of the high street newsagents I visited today has adult colouring magazines.
What is interesting is that I noticed few bookshops and card shops with adult colouring titles than a few weeks ago. However, it is hard to tell if this is a trend because a few weeks ago I did not get to London.
My advice to newsagents is to be thoughtful when ordering. Adult colouring will peak. You do not want to be loaded with stock when that happens.