Riven is a worthy sequel to Myst, and takes the Myst "mystique" to another level with five new worlds and an expanded story line.  The brilliantly realized environments and mood-setting soundtrack draw you in  immediately and keep you there until the sun comes up.  Riven is not for  gamers with short attention spans--simply navigating and charting the  accessible areas of the Age of Riven take patience and time, and solving  what I would characterize as the two major puzzles requires all of the  intelligence and tenacity one can muster.  As some reviewers have said,  having played Myst first is helpful background to have, but this is not  because the puzzles of Riven are similar to those of Myst, but because Myst  will acquaint you with how the creators conceive puzzles, and heighten your  sensitivity to factors in the environment that bear noting and  investigating.  I gave Riven 4 stars, rather than 5, for two reasons: (a)  one of the major puzzles is sound-based, and after some long and  frustrating efforts at solving it on my own, I obtained some hints on the  internet and found that the solution required matching up particular sounds  from the game that, in fact, simply did not match up (at least not in the  version that I bought); and (b) one other crucial clue is a tiny, blurry  image.  In these respects, I felt that the creators did not play fair.  Two  other points:(i) contrary to what some have said, it is indeed possible to  lose this game and meet an untimely end, so be careful out there, and (ii)  recognize that the CD-Rom version is on 5 discs, which need to be changed  every time you travel from one world to another--if you have a DVD-Rom  player, by all means spring for the DVD version, which consists of one  disc.