There isn't much I can add to what other reviewers have said other than concur that this is a fascinating book. The challenges that faced the Nobel Laureates, scientists, engineers, managers of American's largest corporations, and military were beyond imagination. Groueff does an excellent job developing character profiles of people involved in the Project -- all in brief sketches.
You will especially enjoy this account if you have ever visited or traveled through Oak Ridge, TN, Hanford, WA, Los Alamos, NM, the University of Chicago, the old Woolworth Building in New York, DuPont Chemical Company, the American Chicle Company chewing gum factory in New York... well, maybe you get the idea how varied the real story is.