This game picks up where the last left off. I would strongly suggest that you play the first game through (And TOTSC if you have it) then port the character into this game. That way there is something of a continuity between the two games. To be honest, I can barely remember what happened in this game as compared to in Throne of Bhaal, but as I remember it, this game is just much improved from the last one. The best thing about this is the huge number of side-quests that are littered throughout the game. If you don't do these, it doesn't matter diddly squat, but you are going to find the game really hard later on. Find these and complete them wherever possible.
Summary: One of the best RPGs available, buy it witout question if you are a fan of the genre
Graphics: 9 (much improved over the last one)
Sound: 9 (very crisp and clear)
Gameplay: 10 (you'll spend a LONG time playing this)
Longevity: 10 (you'll spend a LONG time playing this)