I did finish the book. Sheridan had some quirks for sure. If he didn't like an order he would ignore it. Grant spent half a year trying to get him to cross the Blue Ridge and attack Confederate supply lines. On the other hand, if the order was to move out at 5 AM, Sheridan's men would be mounted up and ready to roll. He had paid attention in his West Point surveying classes and was a great reader of topography. He could read a map and knew how to use it.
The book really highlights the last few weeks of the Virginia campaign, when Sheridan did finally cross over the Blue Ridge, caught up with Lee's forces and was everywhere, driving in Lee's scouts and flanking forces and seizing all the supplies and transport he could.
Morris, the author, is pretty candid about the atrocities committed by Indian war parties when they captured settlers. You don't get to read that side of the story much any more. War is hell, as they say. Sheridan understood supply and provided material support and protection to the buffalo hunters. He also brought back one of his cavalry commanders, Custer, in whom had had a great deal of faith.
The book covers his later years - Sheridan was military governor of Chicago after the great fire; he was in charge of breaking the Pullman Strike and smashing the union that called it; he was General of the Armies.
This book is a great read
jn