I did check out the dover press site, my wife asked me what I was looking at and I told her adult coloring books, her reply porographic? I showed her no not pornographic, she still shook her head and said still not right. I think it is one of those generational things if you are over 35 or so you don't get it. I colored with my kids when they were young, I never considered coloring on my own or getting my own coloring book.
How is this any different than sudoku, crosswords, or knitting? We all have some time killer we do to stimulate the brain. Parker still got a like too for the hilarious comment.