Rewritten and reillustrated, the second edition of this book covered much the same information as the first edition.
There never was a GURPS Middle Ages 2.
From the back:
"Welcome to the age of chivalry, fealty and piety. GURPS Middle Ages 1 takes you to the rich, dark world of medieval England, where heroic knights fight for King and God, nobles trade favors and treachery, and peasants work the land.
"GURPS Middle Ages I covers the Saxon Kingdoms, Norman England and the High Middle Ages. Each has a distinctive flavor and campaign style – combined with the cinematic "Hollywood Middle Ages," they provide a complete guide to medieval roleplaying."