From the publisher's webpage:
Enhance Your Game!
Enhancements are useful tools, providing unlimited ways to modify advantages. GURPS Power-Ups 4: Enhancements adds to the material from the GURPS Basic Set to provide new and powerful options.
This is a one-stop compendium of all general enhancements introduced after the Basic Set was released -- over 50 total, including several never before seen in any other GURPS supplement! Each enhancement is classified so the GM can know if it's benign, game-breaking, or somewhere in between.
You also get extensive guidelines, advice, and rulings on how to handle tricky enhancements. Meta-enhancements provide a way to customize new classes of abilities easily, the Cosmic enhancement is discussed in depth and fleshed out with several new variants, and the rules for modifying existing damage are greatly expanded and clarified.
Finally, you'll find a table of every enhancement -- including ratings for those classic abilities. Now you'll always know which enhancements are trouble!
With GURPS Power-Ups 4: Enhancements, you'll unlock near-infinite possibilities to augment your advantages. Forget those spam e-mails promising enhancement; this is the real deal!