Uru quite simply fails as a good installment in the Myst universe.
Uru begins with you creating your avatar, and then you're dropped in the middle of the New Mexico desert near "the Cleft" where you'll meet a strange man who gives you some cryptic details about your grand quest. Finding and touching cloths. And no, the story does not get more interesting. Uru wasn't designed to be a single player experience, so Uru's offline mode is simply a bunch of worlds loosely connected by a thin string that could be called a "plot". Uru without a doubt is the weakest Myst game in terms of story.
The gameplay in Uru for the most part remains true to the series. You explore large (though quite dull) ages, and solve the usual puzzles. Unlike most games in the series, though; Uru isn't simply point and click. Like realMyst and the most recent Myst V: End of Ages; Uru lets you go anywhere you want in full real time 3D. Uru also allows you to jump which is annoyingly necessary for certain puzzles.
The graphics are great. Most of the time the textures and area design looks convincing and realistic. There are moments where one of those two things don't quite live up to the rest of the game, but fortunately they are few and far between.
The audio is satisfactory. The enviromental audio is as usual excellent (though quite loud at times); as are the generic sound effects. Uru also has footstep sounds which were for one reason or another missing in Myst V. The music in Uru is okay; it's not the worst of the series, but it's definately not the best.
It's hard to recommend Uru unless you're a die hard Myst fan. Sure, there is Until Uru (a substandard placeholder for Uru Live) and always the possibility that Uru Live will return, but as of right now all there truly is, is a mediocre single player game that only has graphics to support it. If you're looking to get into the Myst series try one of the actual Myst games and give Uru a pass.