Ant is one of those technologies that has an excellent manual and API online. This sets a higher standard for a book so as not too just duplicate the Internet content. "Pro Apache Ant" meets this challenge.
The author walks you through a good number of the Ant tasks with examples and tips. The attributes are provided for common tasks, so you have a physical reference. The author refers you to the manual for some of the less common tasks. A summary of ant-contrib is provided since it is such a standard library. The author points to the Internet for a list of optional tasks.
This book assumes you know Java and the packaging process. In other words, you should know what a jar and war are to understand the sample application.
After walking through the common tasks and incrementally building a sample build.xml, the author delves into some more advanced topics. Included are how to refactor a build file, accommodate large projects, custom tasks, mappers and how to use the Ant API from a Java program.
The book doesn't have any fluff. It starts with an introduction to Ant and Ant's benefits. After a detailed explanation of how to install Ant, you see the first Ant task. I recommend "Pro Apache Ant" if you are getting started with Ant or want to know how to use it more powerfully.