The brave deeds and alien invaders in this novel could easily mark it as a simple adventure tale. But underlying the exciting plot are some deeper themes and questions, which will be apparent to the more thoughtful reader. The Slavers were sent by the Vlantis, inhabitants of a distant planet, to exploit the mineral resources of Earth.

And because Earth's inhabitants are smaller and weaker than the Slavers and unable to speak their language, the invaders considered them expendable vermin. Thus, humans can be killed, enslaved, and used for grisly biological experiments with no more hesitation than using rats. Indeed, Finn at one point discovers that the Vlantis' translator uses the terms "man" and "rat" interchangeably.

Comparisons with many episodes in human history are inescapable. Groups of humans driven by dreams of territorial and/or economic gain have pushed aside, enslaved, or simply killed less powerful...