So I am working on my 3rd coloring book - two horses and now a puppy & kitten one (per my daughter's request). I find it very fun to do and I try to make my own spin on a coloring book to make it slightly different than what is offered by others. I find my second book, Horses in Art, is geared more toward older kids or adults due to some of its intricate lines. All images were taken from The Met's public domain website and it's incredibly awesome they opened up all these works of art to the masses.
One thing I've encountered is during my second book published on Create Space, the merger with KDP went final. I was able to move over my coloring books relatively easy. EXCEPT for the cover. The problem I ran into was the cover selection for designing your own is far inferior in KDP than it was in Create Space. It's unfortunate that we're losing a platform that had more selections. I tried to be so positive when everyone else around me seemed to be panicking because of the merger.
I am still in the process of figuring out how to recreate my covers so they match what was created in Create Space. I had such good hopes. So for now, I will reserve judgement until later.