Serenity RPG

From the web:

The Serenity Role Playing Game lets you re-create the action of the 'Verse, the unique and exciting science-fiction setting created by writer/director Joss Whedon in the television series Firefly. 

Everything you need to get started is in this book. Add dice, friends and your imagination. Fly a ship out into the Black, take jobs as they come, and make sure you get paid!

Features 3 difficulty levels for adventures (depending on the experience of the characters and their players): Greenhorn, Veteran, Big Damn Heroes.
From back of book:

• A self contained role playing game. All the rules are provided for both players and Game Masters!
• Full character creation rules, plus fifteen sample characters, including the crew of Serenity.
• Complete details on spaceships, guns, and technology.
• Emphasis on story, action, and character development with easy-to-learn rules.
• Game details, descriptions of the characters, and settings from the film!