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Amazon
The Witcher 2: Assassins of Kings Premium Edition has been fluctuating between prices.
Steam
The Witcher 2 is also on sale for the same price at Steam.
This is a great deal on the newly released game. CD Projekt just put out patch version 1.1, which removes the DRM from the game. TW2 has an 88 metascore.
Even Obama has a copy of the game :P.