These are from the Georgia archives, but may be useful for understanding the geography of the book.
This one shows the roads, as the were supposed to be right after the end of the Civil War. Note that there is a line which goes from Marietta to Jackson. It roughly follows the Silver Comet trail.
By 1874 there is a marked increase in the roads near Rome and Cartersville. Part of that triangle goes just one side of Snake Gap, where Sherman's men looped around our boys at Resaca. The road from Marietta to Jackson is gone. I wonder why. My guess is it wasn't real or had been damaged too badly by Sherman's merry gang of vandals. The road to Charlotte is almost done. That's the main AMTRAK route today.