The idea here is that you give the parents a creative outlet when they’re reading children’s stories to their kids. So the book contains queue’s which the reader has to make a story with. Or maybe a skeleton story with large blank bits which need to be filled in. Something like “They landed on pirate island, the docks were …. <describe docks>”.
It’s like role playing or theater sports style children’s books. I think the parents will like it because they can really have a bit of fun with it, and they’ll get great reuse out of the books (the story can be different each time). The kids will love it because the parent’s will get more involved in the story (and maybe the kids will too!).