Fragged Empire Second Edition: Rule Book
Fragged Empire makes use of its own unique classless rule system that allows for a large amount of customization, not just in how Players build their PCs, equipment and spaceship, but also for the GM and what kind of campaign they want to run. Fragged also seeks to liberate Players by allowing them to construct a wide variety of characters (rich or poor, bipedal or monstrous, etc...) and party compositions (a party of soldiers, a team of scientists, a smuggler crew, etc... ).
Fragged has an accessible medium-crunch rule system that respects both the narrative and mechanical sides of RPGing, and makes use of a 3d6 core resolution mechanic.
To fully enjoy Fragged Empire 2nd edition, you will want the Rules and Setting Guide books.