It is a very good game, but it is not for anyone who already owns the original Crysis unless it is very cheap.
Because my computer can play Crysis at the high settings, but not very high, I am not sure what the physics would be like on very high, but it seems that they are a wee bit better in this game. A few new weapons and vehicles have been introduced like a grenade launcher (weapon) and a hovercraft (vehicle) even though some of them are not very note-worthy. The story is not as good as in the original game, but it is still nice to see Psycho's own tale during that time on the Island in the original Crysis.
Even though, like in the original Crysis, most areas are large, they still seem to feel too linear compared with its predeccessor's. Nevertheless, most of the level designs are actually even better than in the original, like that part when you were on the train and also in the mine. Even the short part inside a large frozen ship was fun while I was in it. The enemy AI are easier to kill so this would be good for beginners (but to understand the story without playing Crysis, read its plot on wikipedia).
Perhaps what really turns me off from this is that there is nothing really new to the gameplay. Even for an expansion, it still feels like the gameplay did not have much improvement. Regardless of all that, if Crysis is too much for you to handle, start with this game since it is a bit less demanding and less scary too (Not to say that Crysis is a horror or anything like that).