Everything you ever wanted to know about the Empire of Steel, but now in MODERN d20 format. Government, how the emperor is selected, why there are always three princes, why the empress is not always the wife of the emperor but sometimes his daughter or sister, the military nobility, military academies, the difference between warriors and civilians, the warrior colonies, military ranks and promotion, military awards and decorations, the Knights Paladins (the emperor's personal inspectors and auditors), Klingon religions (you thought that 30 billion Klingons all went to the same church?), the intelligence services that spend most of their time spying on each other, data on dozens of Klingon ships, and much more.
You will need a d20 modern core rulebook to use this book. You don't absolutely need a PD20 Prime Directive Modern Core Rulebook, but some of the material won't make much sense without it.