Heya,
^- As mentioned, stand alone.
But save your $30, it's shorter than the first, doesn't add anything to the concept of Crysis's gaping hole of a story line and will soon be available in the trio-pack when they release the Prophet version of Crysis, which will also not be worth the money. When you can get all three in a box together or on a Bluray for like $10, then buy them. Otherwise, just use the Demo as a benchmark and move along. Your $30 will thank me.
Very best,