2 Books Found

Based on your description:

"I don't really remember the plot except for it's from a child/teens POV and them and their sibling(?) get kidnapped, and near the end of the book they're at this abandoned theme park trying to escape. I remember that the cover was pretty plain, it was a solid color (maybe purple?) with a small drawing, and I think it was a car. There was more than one book…"

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