The art work is fantastic and well worth the price, or lack of price. Its a great way to get the atmosphere of the story out where people can appreciate it. The public doesn't care how it was made, the question for some people is whether it is "art" or not, which has nothing to do with publicizing the story.
A long time ago, as evidenced by book covers, one didn't judge a book by it's cover, there wasn't much to it. That's all changed now. A flashy book cover gets attention. Adding artwork to the story was always a positive touch, but expensive. That's all changed now as well. You can keep banging out pictures until you get the ones you want.
I remember the best books (what I liked) at relatives homes, from when I was a child, had a really good, detailed, color illustrations, protected by a thin tissue paper, one picture for each chapter. AI art could easily make this practice a part of producing a book once again.