This book is fantastic. I’m only a tester to the extent that everyone doing XP is a tester but I found many valuable things in this book. There are excellent chapters about how to estimate and plan releases and iterations, including excellent tips on finding hidden assumptions in your stories. I like the book so much that I just bought a copy for a tester who works for me and told him to go home, read it, and not come back until he has so that we can discuss how to put some of the book’s advice into practice. Everyone working on an agile project (not just XP and not just testers) will benefit from this book. It is one of the best–written and most useful in the entire series.