Dick, the book is "Rebels Valiant: Second Arkansas Mounted Rifles (Dismounted)," by Wesley Thurman Leeper [Pioneer Press, Little Rock, 1964]. The LCC Card No. is 64-8219. 328 pages.
It's been out of print for a long time, but if you can find a copy it's worth shelling out quite a few pesos for. It's a pretty detailed book, but it's not footnoted and has only a general sort of bibliography at the end. The author spends a lot of time discussing details of Company G, which included some of his ancestors. There's a complete regimental roster, also good records of officer promotions. This is a book that really needs to be reprinted.