I know of a book by Murial Phillips Joslyn about the Immortal 600.
Captives Immortal: The Story of Six Hundred Confederate Officers and the United States Prisoner of War Policy, Joslyn, Mauriel Phillips (Shippensburg, PA: White Mane Publishing Co., Inc., 1996)

The Immortal Six-Hundred, Murray, J. Ogden (New York: The Neale Publishing Co., 1905; Winchester, VA: Eddy Press Corp., 1911)

The Biographical Roster of the Immortal 600, Joslyn, Mauriel Phillips (Shippensburg, PA: White Mane Publishing Co., Inc., 1996)