The Fireball Mystery

This was one of the first full-story books I ever read and also one of the most memorable. For an adventurous child (as most children are), the story contains elements of interest from all aspects. Plot summary: An avid astonomer-in-training and his older sister who live on a houseboat witness a large fireball fall from the sky and smash into the island a short distance away. Unable to get support from the adults, they wait until nightfall to sneak out to the island to investigate. But while exploring and trying to find they crash site, they stumble across something they weren't supposed to see.