William Harris Bragg has researched and written widely about the men and campaigns of the various Georgia state militia organizations. Joe Brown's Pets: The Georgia Militia, 1862-1865 (with co-author William Scaife) provides the reader with an overview of the state militia's role in the Atlanta Campaign, the Battle of Griswoldville during Sherman's March, the Battle of Honey Hill, and the siege of Savannah. Appendices examine the various militia entities raised throughout the war (including rosters and casualty lists) and how the 'melish' were perceived by various groups. Joe Brown's Pets is beautifully put together, richly enchanced with full page photographs, drawings, and maps. An earlier book length study by Bragg, Joe Brown's Army: The Georgia State Line, 1862-1865, is also available.
Griswoldville goes into somewhat more depth on Sherman's March and the titular battle. Although, it has a similar range of photos, illustrations, and maps, Bragg covers the battle itself in only a handful of pages. A short history of the town and its founder is included, as well as a few chapters dealing with George Stoneman's raid. For a much more detailed tactical history (if that's what you want) of the Battle of Griswoldville, I would recommend Gary Livingston's flawed but still useful Fields of Gray, Battle of Griswoldville, November 22, 1864.