Basic Roleplaying: The Chaosium RolePlaying system

Chaosium's BASIC ROLEPLAYING is a core rulesbook that gathers in one place the rules, modules, and options for one of the original and most influential role playing gaming systems in the world. BASIC ROLEPLAYING is designed to be intuitive and easy to play. While character attributes follow a 3D6 curve, most of the other BASIC ROLEPLAYING mechanics are even simpler. Virtually all rolls determining success or failure of a task are determined via the roll of percentile dice.