From the introduction:
What is Mutants & Machine-guns version 3?
Think of Thundarr the Barbarian, Gamma World, Mutant Future, Mad Max, Fallout and post-apocalypse movies and stories.
All you need to play:
This rulebook, friends, paper, pencil, a few six-sided dice and imagination.
Adds new art and incremental rules refinement to the previous version. Version 3.0 (Draft) varies from Version 3.1 (Draft) primarily in formatting and minor typographical corrections.