Can anyone tell me, is this classed as non-fiction?
Maybe. I just didn't buy those books because it was her long time wish, but because I wanted to see if they can help her brain to recover from all those horrible incidents that has been going for past few years. The results were surprising and really promising. Besides the thing I believe it's really good thing to pass time, because it will allow you to express yourself and show your creativity. Also what I noticed was that as an adult you'll put down the colour carefully instead of slapping around just for sake of it.
I have since the Christmas bought two additional colouring books and I am thinking about getting the Alien one for myself. I used bookdepository instead amazon or walking in stores (as I couldn't see them selling any) and they were very good.