While Dragon Ball Z: Battle of Z isn’t set to release until late January, you can try out the demo later today. This rather beefy demo contains a few story stages, online multiplayer (Co-Op and Battle) and allows you to transfer your demo game save to the final game. Sadly those in Europe will have to wait a day, though you can download the North American demo later today or the Japanese demo right now.
If you don’t want to download the roughly 900 MB demo, you can find some footage of the story mode below. It covers a few of the stages and should be familiar to anyone that enjoyed Dragon Ball Z.