You had your adventures on the secret Myst island, you faced the reality of unknown, and now you must to explore once again.
After short introduction, you're given a book with lots of pages that you can, but don't have to read, and transported to the Riven island. Take the fate in your hands once more, and play this sequel where everything looks better than before.
The way of playing is still picture-jumping with animations from time to time, only this time there are more characters involved to talk to. If you enjoyed the Myst, don't miss the Riven.