The Jericho River is more than it seems on the surface and is not just one more adventure story. Advertised to be a subtle teaching of history in an action adventure wrapper, it is certainly that. You experience the history first hand from the characters that are living it and that experience is more real than dates and names in a history book. And while it may be geared to the adolescent reader, it fits the adult fun equation as well.
If you want to look beneath the fun and get philosophical, you can do that too by contemplating one of the great moral themes in the history of man -- the role of science and its impact on human spirituality. Man has embarked on a 2000 year journey to explain the world and, as he has done so, gradually replaced fear of the unknown with science. Where does this process end and what do we have when all is known?