The strength of Java is no longer in the language itself; it's in the Java Platform (the JVM, JDK, and rich frameworks and libraries). But recently, the industry has turned to dynamic languages for increased productivity and speed to market.
Groovy is one of a new breed of dynamic languages that run on the Java platform. You can use these new languages on the JVM and intermix them with your existing Java code. You can leverage your Java investments while benefiting from advanced features including true Closures, Meta Programming, the ability to create internal DSLs, and a higher level of abstraction.
If you're an experienced Java developer, Programming Groovy will help you learn the necessary fundamentals of programming in Groovy. You'll see how to use Groovy to do advanced programming including using Meta Programming, Builders, Unit Testing with Mock objects, processing XML, working with Databases and creating your own Domain-Specific Languages (DSLs).