Betty,

I am not aware of any book specifically written about the 9th Battalion Mississippi Sharpshooters.

There was a Zachariah Lofton listed among the members of the 7th Mississippi Infantry, according to the National Park Service's Soldiers and Sailor's website at http://www.itd.nps.gov/cwss/soldiers.htm. His alternate name is shown as Zack Loften. This may well be your g.g. grandfather.

There is also a website devoted to 9th Battalion Mississippi Sharpshooters at the following website:
http://www.mississippiscv.org/MS_Units/9th_Bn_MS_Sharpshooters.htm

Best regards,

Mike Bailey