1. The Boys of Company K: Ohio Cavalry Soldiers in the West During the Civil War by Lee M. Cullimore (High Plains Press).
In 2005, Robert Huhn Jones's Guarding the Overland Trails: The Eleventh Ohio Cavalry in the Civil War was published by venerable western history publisher Arthur H. Clark. It's a pretty good account of the service of a volunteer cavalry unit on the plains (Wyoming, Colorado, Nebraska, and Kansas) during the Civil War and the Powder River Expedition soon after its end. Cullimore's company history goes even more micro [why Co. K? -- I guess I will find out].
2. Ending the Civil War: The Bloody Year from Grant's Promotion to Lincoln's Assassination by Benton Rain Patterson (McFarland, 2012).