Simple and Conversational
If you were gathered around a fireplace telling an old family story, you might sound a little bit like the narrator in Strega Nona. If you were trying to scare the pants off your friends with one of those "the-call-is-coming-from-inside-the-house" stories, maybe not so much. But if you were just relating an entertaining event that happened in your childhood, yeah—there'd probably be some similarities.
The sentences dePaola uses are simply constructed. They vary enough in the way they're put together to avoid sounding monotonous, but they're simple to read and simple to follow. They're meant to be easily understood.
That's why this book works so perfectly as a read aloud, which is how most people first encounter it. And if you employ a similar simple and conversational style when you tell your story around the fireplace, your friends are sure to be rapt. Especially if you have some pictures to go with it!