This is the Second Edition corebook for the Obsidian universe. This book has all the rules, mechanics, history, setting, and players that are used in the game.
From the back cover:
The year is 2299, and a desperate humanity wages war against the manifested legions of hell itself.
In the final battle, the last vestiges of mankind construct a vast fortified city to hold the daemonic hordes at bay.
Within this city, massive corporations vie for power, Daemonic Kults carve a bloody swath through its citizenry, and technology has surpassed the limits of the flesh.
Take care when choosing your allies,
Even more care when choosing your enemies.
This is the Zone.