Gettysburg is probably his best book, although I must honestly say I haven't read Chancellorsville yet. Gettysburg is THE best one volume history of the battle and is very readable for the novice, but sufficiently detailed to keep the Civil War historian engaged.
Haven't read this yet, but it's on the book shelf...in line....behind a lot of other books....
The first one of his books I read and I was hooked. The missed opportunities for the Union to win the war on this day are tragic...to digress....much like Obama, McClellan was not as smart, or brave as he thought he was. The Confederates fought off a force easily twice their size for most of the day...brilliant defensive generalship by Lee, Jackson and their subordinates.
A good history of a fairly forgotten series of battles. The Seven Days saw the largest Confederate Army of the war in action and represents a few missed opportunities for both sides.
Overall, these books well researched, tightly written and excellent books for anyone getting started reading about the Civil War.