It is more proper in the sense that contractions don't belong in formal writing, though.
True, although I hardly consider LS books "formal."
I guess my issue with it is that it sounds unnatural. I've never heard anyone actually talk like that. Even as a kid, I was also bothered by the short, simple sentence structure, although I recognize that was done for the target audience's benefit.
<3 Bre -- lover of animals, collector of dolls, reader of kiddie books <3