One of the best pieces of parenting advice I ever got was that any book written before the 1950s is OK for your kids to read without your previewing it. Anything after that may have problematic content (there's some historical reason for this I can't remember; decency laws or something). This isn't just for big kid books. I can't remember how many picture books we've brought home from the library that I ended up hiding for the rest of the week. Here's a great article on how children's books have changed to justify and laugh at what would have been considered bad behavior in ages past. I got a kick out of Frances being contrasted with Olivia--my grandma never approved of Frances. She put the bad in Badger back in those innocent 80s.
Olivia, in our house children don't talk to adults that way.