I made a great find two years ago,
"The Headquarters Diary of Edward O. Guerrant, Bluegrass Confederate," edited by William C. Davis and Meredith L. Swentor, LSU Press, Baton Rouge, 1999, a 716 page tome, and I highly recommend as a great read.
Chapter 26, The Battle of Saltville, Virginia, pp. 531-549, and then again, Chapter 31, Defending Saltville Again and the Battle at Marion, Virginia, pp. 599-615.
My ggrandaddy was there with Vaughn's East Tennessee Cavalry Brigade in the 43rd Tennessee Cavalry. CSA.
George Martin