Played it for the first time, after it has been out for over ten years.  Great game.  The puzzles are hard, but not impossible to solve.  If you truly love Myst, then you will certainly love this game.  (Do not use walkthroughs, it ruins the game!)  Also, keep in mind that the 5-CD Riven set is for outdated computers.  It will most likely not run on Vista or XP, at least not without some major glitches.  Wish I had played this sooner.