You ever love a book so much and then watch a film adaptation and immediately hate it because a character voice is "wrong"? Or the room doesn't look right? That's my problem here.
There's also the fact that the original story, which focused more on the family dynamics, is kind of stripped down to two minutes and then exploded into a Scooby-Doo plot about mass hysteria and Reaganomics.
The one good thing is that it makes very obvious at book report time who just watched the movie.