It's mandatory to be boring. Anything else is offensive.

Little kids want to read about flinging poo, farting, projectile vomit, violence, and every possible misbehavior.

Supposed "children's books" are actually marketed toward grandmothers and public school librarians.

What about that Captain Underpants crap? I hated it when I was a kid but it seemed pretty good to the other kids and kind of acceptable to the adults.

Not sure where the other poster lives but the entire Captain Underpants series is in our son's school library. That's where he read the first one and we purchased the rest for him as he's a voracious reader. They aren't the best books but there's a big benefit in the kids having something that they are interested in reading and will read without being pushed.