If you have already pre-ordered the game, you can pick up your beta key beginning on August 9 from your GameStop location. A trailer showing off the 'Wanted' multiplayer game mode can be seen below.
BOOM video 5467
Assassin's Creed Brotherhood continues the story of Assassin's Creed 2, while introducing the aforementioned multiplayer component. It will be released on November 16 for the PlayStation 3 and Xbox 360.