I just reread the series before buying the new book later today. I love them - they are just good stories with good and evil. To fuss and read more into them than that is silly. I suspect more adults read them than children.....I have carried mine around for a few weeks, and a lot of adults have commented that they are looking forward to the new release coming out.
We are at book six, and I haven’t seen stories of children taking them too seriously. In fact, most kids have quit reading them long before the adults.
Lots of spiritual consequences of such things lie relatively dormant from all overt appearances . . . for extended periods of time.
That does NOT indicate harmlessness.