Another book suggestion
Sorry to say I had not seen this report before today and this may be a repeat:
For some interesting information on the Gettysburg battle may I suggest "These Honored Dead" by Thomas Desjardin.
It is not a description of the actual battle but addresses many of the stories/legends/myths that surround it and tries to provide the facts. I found it quite well done.
Certainly hope you enjoy the remainder of your trip.