Per the Neale bibliography, this ex-governor of Virginia (1894-1898) served in the 12th Virginia Cavalry and his reminiscences of their exploits are solid and valuable. O'Ferrall hailed from western Virginia and despite the strong Unionist sentiments in the area, felt his true allegiance to be to Virginia and the Confederacy. He enlisted as a private in the cavalry, quickly advanced to sergeant, and then promoted to major after displaying significant gallantry and promise in battle. O'Ferrall had advanced to colonel by war's end and was in command of all Confederate cavalry in the Shenandoah Valley. He was wounded 8 times during the war, including once so seriously that he was left for dead.
Copies shown here are generally in the $150-250 range and I suspect the book's collectability has as much to do with its Neale Book status as for the material contined within it.