I bought the book because I knew it featured a Union soldier's service in Tennessee, my home state. I wasn't disappointed.
Webb Baker's story doesn't begin with the attack on Fort Sumter. It actually begins with his being a witness to one of the Lincoln-Douglas debates in 1858. His home county in central Illinois was a battleground between the pro-Lincoln north of the state and the pro-Douglas south. He signs up for the army immediately, a Lincoln-man first--only later will his opinions on slavery change.
Three battles in Tennessee are covered thoroughly: Stones River, Chickamauga (yes, in Georgia but following actions in Tennessee), and Chattanooga, the latter of which Baker missed while recovering from wounds at Chickamauga. Bobrick is a big fan of Rosecrans, showing how initially the general took Chattanooga without a major battle, only to have two things happen (1) the far-bloodier events in Vicksburg and Gettysburgh overshadowed the victory, and (2) Chickamauga, where Rosecrans' tactical superiority was thwarted by a rushed advanced.
The book ends with the texts of letters written in 1861 and 1862, the bulk of which are referenced in the book.
One thing that struck me as I read was Baker's thoughts about Tennessee. He liked the weather and the lush farms. I could see him--even as an invading soldier--taking ownership of the state and considering a life here in peace time. This, of course, lends insight into the legions of Union veteran "carpetbaggers" who surged south after the war to try their hands at peacetime occupation.