"The Hole Man" is more than the exploration of a universal theme and more than its characters. It is the conscious creation of an environment that is full of promise of surprises to come. Niven captures young imaginations with a "dance of ideas," and he offers much in "The Hole Man" to take hold of the imagination. For instance, there is a large alien base with.low ceilings and a communal sleeping area. The narrative capitalizes on the attraction that mysterious places have for the imagination. As the base is explored, the researchers discover that "the aliens had been studying Earth during the first Ice Age." They suspect the alien base had been left running for humans to find. One might suspect that the gravity wave device was left so that humans could someday call the aliens. Then, "the backblast never touched the skeletons"; the remains...