OK - I can see that.... but suspense thriller is relative.... it was age appropriate for children. It wasn't "Steven King" dark.
No, not "steven king dark" and I wouldn't take a pre-teen to see most of the movies based on his books. People forget these days, there are books and movies for kids and books and movies for adults (when I say adults, I don't just mean x-rated, but mature themes).
By the way, I'm shocked that nobody has jumped on Dahl for being a Satanist, since he did write The Witches.