From the back of the book:
It is a period of galactic civil war. On one side, a ragtag collection of freedom fighters called the Rebel Alliance. On the other, the terrible might of the Empire, best symbolized by the technological terror known as the Death Star.
An armored battle station the size of a small moon, the Death Star packed enough firepower to destroy planets. Alliance researchers have uncovered many of the secrets of the most devastating weapon in galactic history, and gathered the information together in this one volume. The Death Star has been destroyed, but its legacy lives on.