Andy No. Not at all. This is a novel about how an incomprehensible alien event changes a community and the people who live there. There is no attempt to link what happened to any reasonable scientific theory or fact. The author even goes out of his way to show how clueless the scientists in the story are as to how the alien artifacts function.
Ryan It's difficult to call it hard sci-fi because of the ambiguous nature of the aliens' intent in their visitation; though as the title suggests, earth was just a rest stop on a journey for the aliens. Even harder to call it hard sci-fi because of the nature of the anomalies and artifacts left by the visitation, which often defy physics as we know it. When I think of hard sci-fi, I think of books based on theories, hypotheses grounded in what we know of science, there isn't much of that here. That being said, for how short the book is, it is an outstanding read for fans of all types of sci-fi, and a great look into a society that was essentially cut-off from the world at the time of its writing.