Prof. Allen Guelzo's Gettysburg: The Last Invasion was listed in the July 1 Baltimore Sun as one of the "best new books on the Battle of Gettysburg".
From the Sun:
On the 150th anniversary of the battle of Gettysburg, historians are revisiting the three-day event that was a turning point in the Civil War -- and publishers have released a slew of new books. For my money, there's still no better book than "The Killer Angels" by Michael Shaara, a fictionalized treatment that closely follows actual events, including the stirring attack on Little Round Top. But if you're looking for new reads on Gettysburg and the war, here are some favorites:
-- "Gettysburg: The Last Invasion," by Allen C. Guelzo. The professor at Gettysburg College, which sits beneath the ridge where the battle began, takes an in-depth look at the three days of fighting. This book, which draws heavily on first-person accounts, will get you close to the action.