Several scenarios exist: historical (what acutally happened at the battle) and speculative (fascinating what ifs, for example, a scenario exists for Stonewall Jackson's presence at the battle). The gamer is also allowed to adjust the difficulty level of the opponent (computer) until a better understanding of the game and strategies are attained.
The graphics are excellent and realistic - I have visited Gettysburg 6 times in my lifetime and the game's terrain features are pretty close to the real thing.
There are a few minor bugs, but not enough to detract from the game. Highly recommended. Buy and enjoy!
The main bug I encountered not already mentioned was the enormous amounts of casualties the skirmish formation inflicts, and the minimal casualties suffered. I have patched it, and it still happens. Try the three day battle at the easiest difficulty level with skirmish mode. The enemy, whichever side you choose will crumble. A 7-1 kill ratio is not atypical. At higher difficulty levels, this continues, but the skirmish units are very quickly routed, even if the enemy unit attacking has sufferted large casualties, and I've lost five men. This makes the skirmish the strongest formation, if you have a large amount of troops to hold objectives once they've been routed.
Another problem is that the division, corps, and army commanders, are not very useful, except for boosting morale and rallying troops, and seeing all units under the officer's command.
Also, the lack of friendly fire makes for unlikely movements. You must entirely surround a regiment to have it surrender. When it is routed and has nowhere to run, that is the only situation in which it will surrender. So it pays in the game if you manage to encircle a regiment(s), even if in reality, your own troops would have fired more shots at each other than at the enemy. But if it manages to slip through a narrow gap, which seems like computer cheating, it won't surrender.
And again, artillery and cavalry are not useful. You must mass a large amount of artillery to inflict the amount of casualties a brigade can. The only use is that they lower enemy morale at no cost. They provide opportunities for greater losses as well. Also, it's almost like the computer cheats, when it comes to using a regiment to capture enemy guns, they always run away, or the regiment is "repulsed." Cavalry are only infantry that cost twice as much to lose. They don't lose morale in skirmish mode, but their costliness leads me to pull them off to the or retreat when I have infantry to take their place. They have a speed advantage in column mode that can be used at times to capture unoccupied objectives, such as when a few routed enemy units recover behind your lines.
In the Pickett's Charge scenario, there isn't much Union artillery at the easiest difficulty level, and at higher levels, they don't do the damage that they historically did. It's likely at the hardest level for you to lose disastrously, playing as Union, because your own morale lowers more quickly than that of the computer.
I'd like to reiterate the point already made that the importance of objectives detracts from realism. If you know anything about the Civil War, then you know that, for the most part, successful generals pursued armies and not locations. There are no decisive locations on this map. Lee was trying to push north, and if there are to be any Southern objectives worth a small amount it should be to control roads to the North and the town itself.
The last problem I can think of at the moment is the significance of battle formations. It is difficult to take advantage of holes in enemy lines. You simply amass enough firepower and reserves to lower morale and cause the enemy to retreat, and it's sort of automatic. The enemy is certainly good at finding weak points in your line, however. Also, it is difficult to try moves that could be described as "daring" or "risky." I have attempted to outflank the enemy by swinging an entire brigade(s) to the side of their lines, and the problem is that it takes too long, and the scenario ends before I can get started. Also, realistically, the enemy would remove or realign some of its units from its locations if in a true battle I had troops almost behind it.
Still, given the price now, used or in a store, this game is worth getting. Lots of play on these 3D maps help get you familiar with the battlefield, if you decide to visit. Also, the PDF included has some basic information, as well as battle statistics. If you have a book on the battle, this is a refreshing way to experience it, and, despite the bugs and design flaws-it belongs on the shelf of every Civil War buff and battlefield visitor.