If you have difficulty finding information about your father or grandfather's World War II Army service, a book published last year will help – Finding Your Father's War, A Practical Guide to Researching and Understanding Service in the World War II US Army by Jonathan Gawne, 2006, Casemate Publishing, ISBN 1-932033-14-9.
The author started searching for his father's war record after his father’s death. Earlier questions about the war had always resulted in his father saying he didn't remember. The author's journey resulted in this excellent reference work on individual and organizational records. Although the book lacks an index, the author's extensive use of appendices provides access to needed information. In his introduction, the author writes: "As a final piece of advice on how to try to learn more about World War II, my father once told me that all you have to do is read Ernie Pyle's stories and look at Bill Mauldin's cartoons." I would add to that advice, check out this excellent resource on the Army in WWII.