A metafictional exercise. It's hard to say anything that hasn't been said already, particularly in Drew Cook's excellent and lengthy analysis. But it's crucial to me that, as pointed out by others, the game does have a hidden Nazi mode in it: (Spoiler - click to show)all you need is to type "join the ss".
I basically agree with Cook's essay linked above; I think the version of the game without the hidden Nazi mode would be more compelling. The actual Nazi mode is badly done and punctures the fear, the horror, the elaborate, multilayered metafiction, with jokey references to the Holocaust. Compared to what's there, it would've been better if the Nazi mode was left to the reader's imagination. Nonetheless, I do think the game has spawned some interesting discussion and analysis.