Reddit reviews Hallowed Ground: A Walk at Gettysburg (Crown Journeys)

The most-often recommended single volume is Battle Cry of Freedom.

If Gettysburg is an interest, I found Hallowed Ground by the same author to be a good read. More exhaustive is Sears's Gettysburg, which helped me to understand a very dynamic picture.

Finally, we often get inquiries about the roots of the war. The Pulitzer Prize winning
Impending Crisis is first-rate.