So maybe I was wrong

I read several pages of Son1's library book about Calvin and Hobbes when we first got it. It seemed ok. He's been reading it EVERY DAY. But I recently found out there are some expressions and vocabulary in it I'd rather my son not learn just yet, so I have decided that it is really not appropriate for a five-year-old. I was never that big of a Calvin and Hobbes fan, but I used to read it once in a while. I guess my memory must be failing me...