According to a news release from GameStop, it'll feature the first public, playable build of Call of Duty: Advanced Warfare in North America. So if you want to get a headstart on those killstreaks, this might be a way to go about it.
Of course, if you're not particularly interested in Call of Duty:
Tickets for the expo can be purchased through GameStop's website. Until August 15, general admission tickets will cost $40, while a VIP pass will run $110. After August 15, the cost of general admission rises to $50, while the VIP jumps to $125.