A mythical plot and extraordinary graphics are what Riven has to offer.
The story is intricate and several plot twists, revealed through reading scattered journals, adds an interesting dimension to the game. This time you meet with the father of Atrus, Gehn, revered as a demi-god in a world that is slowly falling in pieces.
The graphics are as astonishing as ever and their realism, combined with the fantastic creatures and landscapes, give the player an extraordinary feel of another world. The filmed actors have been nicely integrated to this world. The music and sounds also participates in creating the mystical atmosphere the Myst games are so renowned for.
The puzzles don't take as much place as in Myst but rather leave more place to exploration with a nice set of islands and transportations to ride across them. It took me a long time to truly enjoy playing Riven because of the long distances (you often need to travel back and forth) and the difficulty of the puzzles (without a guide) but it only gave me a greater feeling of achievement.
So I really recommend this game to all those who enjoy laborious puzzle solving and fabulous worlds of imagination. Just make sure you're patient enough unless you don't mind relying on walkthroughs.