Storywise plays the addon to "Oblivion", ie the underworld no longer exists and whose Queen Lillith (I think she survived) appeared in "Shivering Isles" not to, instead, there is now exploring two islands and a story that is not might be clichéd. Graphically, the addon is eingegittert in the main game.
Overall, a solid extension, which provides more hours of gameplay and me personally something looks artificial, as well as the tough story. That is why 3 of 5 stars.