Gothic 3: Forsaken Gods is a very good game! It got good gameplay and a great storyline! It's only flaw is all the bugs!
It shouldn't be any problem understanding the game even if you haven't played Gothic 3, but I recommend doing so anyway.
The controls in Forsaken gods is the same as before, and imo, it's quite easy controls. (But then again, I have played all Gothic games)
You start out in a small village, which you have saved from the orcs in the past. There you have to earn the trust of people, just like you'll have to do later in the game too. People don't know you're the nameless hero who saved Myrtana (Gothic 3) and Khorinis (Gothic 2), so you'll have to work you're way up.
The graphics in the game is great, and the music and the sounds are just awesome!
But.. there's always a but..: The game is still full of bugs. I mean, not as many as before, but there's still bugs out there. And it's also quite laggy, even though you turn the graphics down to the worst. In fact, I don't noticed a difference when I turned the graphics to the lowest, as it was still just as laggy as at the highest. So, they still have work to do on the engine.
So, I have given this game a 9/10, and if they remove the bugs and lag it will get a clear 10 from me!
I know lag and bugs is supposed to take the rating down a lot, but the game is so awesome that I can continue playing in spite of all these bugs.
So, worth the money and the time! :)