From the back of the book:
Through the looking glass...darkly.
Haven't you ever wanted to phaser the captain, level a helpless planet, and steal your weight in gold-pressed latinum? Now you can—on the other side of the mirror. In this setting book for the Star Trek Roleplaying Game, you can bring Federation ideals of justice to the Mirror Universe, or revel in your own character's dark reflection. Prowl the Terran Empire with Captain Kirk of the I.S.S. Enterprise, or crush puny Human rebels with Intendant Kira of the Cardassian-Klingon Alliance. So grab your agonizer, grow a goatee, and watch your back—because in the Mirror Universe, nothing is what it seems...
Through a Glass Darkly: The Mirror Universe includes:
Complete setting information for the Terran Empire from Star Trek and the brutal Alliance from Star Trek: Deep Space Nine.
Rules and guidelines for creating your existing character's mirror image.
Everything you need to play a "Mirror series," including new skills, cruel traits, and the malign Wheel of Comeuppance.
Star Trek RPG rules and statistics for the agonizer, the Tantalus Field, and the deadly devices of Imperial Security.
Unsolved mysteries of the Mirror Universe to explore on your own or use in your series.