This book is a must read for anyone who works in a multithreaded application, which turns out is a lot more frequently than you might expect. If you work in a J2EE container, Swing GUI application, or any kind of concurrent system, this book will give you the know-how to create effecient, scalable, and correct programs.
It helps dispell common misconceptions about concurrency, and showcases the improvements to concurrent programming in Java 5.