There are several Rock Band games. Rock Band 1, Rock Band 2, Rock Band Track Pack Vol. 1, 2, Classic Rock, and AC/DC. And on September 9th, Rock Band: The Beatles will be out, (and I already reserved a copy, which you can pretty much do at any game store).

The only way you would be able to buy Rock Band is probably online at eBay or amazon. I don't believe it is sold in stores anymore except if you have Rock Band 2, you can buy the Rock Band track pack and download the Rock Band songs.

As of today, there are just over 800 total songs available for download and for purchase on track pack discs for the Rock Band video game. Slightly fewer songs at just over 650 are available for the Wii version of the game.

The song "Run To The Hills" by Iron Maiden was in Rock Band 1 and is available in the Rock Band: Iron Maiden - Flight 666 Downloadable Track Pack.

Its not on the actual game but it's on the expansion pack "Track Pack, Volume one"