This book investigates the statistical probability and catastrophic potential of near-Earth object impacts on our planet. John S. Lewis, a professor of planetary science, utilizes geological evidence and orbital mechanics to argue that the threat of asteroid and comet bombardment is a significant, albeit overlooked, risk to human civilization. He provides a framework for understanding the history of planetary collisions and the technological requirements for planetary defense.

Experts in planetary science recognize this work as a foundational text for understanding the mechanics of impact hazards. Readers frequently note the technical clarity of the prose, which makes complex orbital dynamics accessible to a general audience.