From the publisher's website:
GURPS Martial Arts brings fighting styles from throughout history to Fourth Edition. From popular Asian bare-handed techniques to European combat arts to fantastic non-human training, this book balances realistic historical schools with cinematic feats from Hong Kong, Tokyo, and Hollywood. Recreate the greatest fighters in the world, or create a style to fit a new campaign, Martial Arts has the techniques and guidelines you need.
Not all combat options map to techniques and styles, however. Many require extensions to the combat system itself, so Martial Arts expands on the combat and injury rules from GURPS Basic Set. Some of these additions are highly realistic, while others are extremely cinematic - but they're all optional, allowing the GM to decide which rules apply. Customizing the GURPS combat system has never been easier.
This book replaces and expands on the information and rules from the previous edition of GURPS Martial Arts for Third Edition.