I was hoping someone else would come up with THE classic :- http://www.textbookx.com/detail-book-0817350861-The_Mound_Builders_A_Reconstruction_of_the_Life_of_a_Prehistoric_American_Race,_Through_Exploration_and_Interpretation_of_Their_Earth_Mounds,_Their_Burials,_and_Their_cu.html is probably the one you want
For a history of their exploration http://www.textbookx.com/detail-book-0821408399-The_Mound_Builders.html
http://www.textbookx.com/detail-book-059530561X-The_Mound_Builders_of_Ancient_North_America_4000_Years_of_American_Indian_Art,_Science,_Engineering,_&_Spirituality_Reflected_in_Majestic_Earthworks_&_Artifacts.html sounds like a New Age view (hardback http://www.textbookx.com/detail-book-0595661815-The_Mound_Builders_of_Ancient_North_America_4000_Years_of_American_Indian_Art,_Science,_Engineering,_&_Spirituality_Reflected_in_Majestic_Earthworks.html)