This book investigates the persistent and catastrophic threat posed to Earth by near-Earth objects, specifically comets and asteroids. John S. Lewis, a professor of planetary science, utilizes data from space exploration and terrestrial geological records to argue that impact events are not merely historical anomalies but recurring phenomena. He presents a framework for understanding the solar system's history through the lens of bombardment, challenging the notion of a stable, peaceful planetary environment. By synthesizing paleontology and planetary geology, Lewis demonstrates the correlation between cosmic impacts and mass extinction events.

Experts in planetary science recognize this work as a significant contribution to the public understanding of impact hazards. Readers frequently note the clarity of the author's scientific arguments despite the technical nature of the subject matter.