Published in 2002 by Manning Press: http://www.manning.com/hatcher/ (Amazon: ISBN 1930110588 )
Written by Erik Hatcher and SteveLoughran; certainly the largest book on Ant to date, and probably the best selling.
Tries hard to discuss Ant best practices, and encourage test-driven development and deployment, whenever appropriate.
Their AntPractices section is now hosted on the Ant site: http://wiki.apache.org/ant/TheElementsOfAntStyle