From publisher blurb:
The Advanced Mutant Companion is a collection of optional rules compatible with Mutant Future. Enhance your characters with new mutations and races, as well feats and backgrounds. This book includes:
74 new mutations. New physical, mental, and plant mutations. For ease of use, they have all been organized into random tables with the original Mutant Future mutations.
5 new races and 2 revised races. Play as aliens, cyborgs, and others. Pure humans and mutant animals are now more exciting too.
100 backgrounds. The background system is a flexible skill system that encourages role-playing and character development.
18 feats. Characters can earn fun new features like pets, followers, holdings, renown, and more.
New equipment rules. Finally, characters have something cool to spend their money on.