I research the regiments of Cumming's Brigade, Stevenson's Division. The division is not forgotten. I also collect information on Pettus's, Reynolds', Brown's, and Vaughn's Brigades as I come across it.
I will have a reminiscence of a 39th Georgia soldier complete and I am looking for a publisher at the moment.
The book "A Fit Representation of Pandemonium: East Tennessee Confederate Soldiers in the Campaign for Vicksburg" by William D. Taylor was published in 2008.
The AOT historiography suffers overall for several reasons and that began immediately after the war itself. One reason why you see a distinct discrepancy in Vicksburg AOT regiments is that many of the men deserted while they were on furlough. So, many of the regiments have a plethora of material up to Vicksburg but practically none afterwards. They reorganized in September 1863 as shells of their former selves and couple that with the meatgrinder of the Atlanta campaign you don't have many remaining to tell the tale.
If you "google" each of the regiments in Pettus's brigade individually you will see a little primary source material.
I hope this helps.
Gerald D. Hodge, Jr.
M.A. Military History - Civil War Concentration
Research - Preservation
Historian: 39th Georgia Volunteer Infantry Regiment