There are a few points where I take issue with Mr Keegan or would welcome elaboration not present in the book. His assessment of commanders evaluates Genl Thomas (Stonewall) Jackson as having improvisational abilities comparable to Germany's Erwin Rommel. Perhaps that's not easily done in an overview: the relatively few endnotes leaves me with more research than I have time to do. His comparison of Genl McClellan favorably with the Third Army's George Patton, endnotes or no, does not convince. I cannot conceive of Patton establishing a beachhead behind Richmond in the spring of 1862 and not immediately going through Genl Joseph Johnston's lines like the famous crap through the goose -- that Patton would also have fired Genl Butler for getting corked up at Bermuda Hundred the second time the Army of the Potomac paid for that real estate, but he's not making comparisons to Genl Grant. His evaluation of outstanding commanders makes no mention of Genl Longstreet, an odd omission given his repeated use of lessons forgotten after 1865 that commanders in The War to End All Wars had to relearn on the Somme and at Verdun and Gallipoli.
The book hints at topics for future research. The concluding sentence is "American socialism was stillborn on the battlefields of Shiloh and Gettysburg." Elsewhere, he refers to partisan warfare in the rebellious states. Deserters from the rebel armies, while not explicitly aligning themselves with the Union, nevertheless fought militias detailed to return those deserters to the service of the rebellion. Perhaps the reluctance of Genls Lee and Johnston to accede to Jefferson Davis's calls for partisan warfare reflected an awareness that gray-on-gray fratricide would harm whatever Southern cause remained and only assist whatever reconstruction efforts were being implemented from Washington. Consider also this British understatement on page 323. "[Genl McDowell] had served a year with the French army, until 1870 thought the best in the world."
(Cross-posted to Cold Spring Shops.)