Riven is a satisfying sequel to Myst.
Riven is set some time after Myst. After growing bored of wandering Myst and the other ages you return to Atrus who is grateful to see you and sends you to an age called Riven with several tools. Your quest is to rescue Catherine and capture Ghen. My problem with this setup is it lacks the mystery that I loved about the original Myst's plot, but Riven still contains an interesting, and well thought out story.
Riven's gameplay is the same as the original Myst's. You'll need to solve puzzles to progress through the plot, and read journals to understand more about it as well as get clues. The thing about Riven is that it is a lot more difficult than Myst; a good portion of the puzzles are extremely frustrating and can often leave you with less hair than you had. If you like difficult puzzles then you'll love Riven.
The graphics are a mixed bag for me. While they are photo realistic the lack of variety turned me off. Most of Riven consists of staring at rock and sand for hours on end, and quite frankly I don't find rock and sand very beautiful to look at. Riven does get praise from me in this area from looking so real, however.
The audio is excellent just like in the original game. The game pulls you in with its ambient sound effects, and sound effects in general. Unfortunately the music while ambient doesn't really excel at anything other than being quiet. Some people like the music's quiet nature, however; I for one think it makes the soundtrack quite forgettable. I still remember the music from Myst; I can barely remember anything from Riven's score.
Riven is a good sequel to Myst. It has photo realistic graphics, challenging puzzles, and an interesting story. If Myst was too hard for you then stay away from Riven. Fans of the series tend to praise Riven as being the best, and while I respectfully disagree I can see why they may think so.