When I was around 12 years old my father and I were having a conversation. I don't remember the topic, but at one point he gestured toward the bookcase and mentioned a couple of books that he thought were not appropriate for someone my age. Can you guess what I did the minute he wasn't looking?
Trying to prohibit children from reading certain books is futile. If you really don't want them to read a book, tell them they are required to read it. Better yet, have a teacher assign it as homework. Then you can be sure they won't read it.
My comment was tongue-in-cheek. I did read a couple of the books many years ago. The only title I remember is "The Lion, the Witch, and the Wardrobe." I remember few details from the story.
I found the stories only mildly entertaining. Fairy tales are not my favorite form of literature. I did not associate them with Christianity or any other religion or ideology. The idea that the lion was Jesus Christ never occurred to me.
I see no harm in allowing children to read The Chronicles. If that leads you to classify me as a "Christian Nationalist" (whatever that is), then that is your prerogative.