From the back of the book:
A terrible civil war burns throughout the galaxy. A rag-tag group of freedom fighters has risen from beneath the dark shadow of a tyrannical Empire: against all hope, they have dealt the oppressors a mighty blow.
Throughout the vastness of space, heroic beings engage in a desperate struggle against the overwhelming might of the Empire. They are ill-equipped and pitifully few, but their courage and determination has fostered new hope for freedom in the galaxy. These are the men, women, and aliens of the Rebel Alliance.
This sourcebook is set between the end of Star Wars and before The Empire Strikes Back. It details the extrordinary Rebel Alliance from top to bottom. You will find explanations of procedures, diagrams, descriptions and accounts of everything from as-yet-unseen ships, vehicles and equipment to the overall political and military hirarchy, underground operations and safe worlds.