How can I learn more about the history of the project?

For a helpful overview, see Barbara B. Oberg and James P. McClure, “For Generations to Come”: Creating the ‘Definitive’ Jefferson Edition” in  A Companion to Thomas Jefferson, ed. Francis P. Cogliano  (Wiley-Blackwell, 2012). 

See also, Mark F. Bernstein, “History, Letter by Letter,”  Princeton Alumni Weekly, May 14, 2003