From the back cover:
The Underground Player's Handbook provides you with scores of new rules that will prove useful to street soldiers and insurrectionists alike.
- Expanded character creation rules, including rules for creating non-boosted PC's and non-veteran boosts.
- New enhancements.
- Expanded rules, and new bonuses and limitations for existing enhancements.
- New rules and uses for reward points.
- A guide to the street slang of 2021.
- Eight new character archetypes.