Probably still the best biography of Lee was entitled "Robert E.
Lee", in four volumes, by Douglas Southall Freeman. Freeman also
wrote the excellent study of Lee's Army, in three volumes, "Lee's
Lieutenants", and a multi-volume biography of Washington. Southall
was a Virginian, and lived long enough ago that some Civil War
veterans were still alive, and there were many people around who
remembered the war and its participants.