"Myst" first came out in 1993, and changed the games industry, making CD-ROMs into a popular format and selling some 10 million copies. The graphics, while technically dated, are still brilliantly art-directed. The music is also excellent, and the puzzles, while fairly difficult, are diverse and logical, and definitely solvable, especially with the Masterpiece Edition's embedded hint guide!
This game was followed by "Riven" in 1997, which was done with over ten times the budget of Myst and photoreal graphics. Riven is also an exceptional game with a superb story and puzzles seamlessly integrated into the gameworld - and, of course, wonderful sound design.
Three more sequels followed Riven, all of them great games. There's also Uru, which is/was a huge, realtime 3d Myst MMO, but it was cancelled. Cyan Worlds (the Myst creators) plan to rerelease it as an open-source game, as soon as they can raise enough spare cash to assign the needed staff to do so.
So, basically, by buying Myst and Riven here at GoG, you're not only getting two legendary classic games that are well worth it in their own right, you're also speeding up the release of a Myst MMO and its game engine, world creation toolset, etc, as freeware.
In any case, Myst is a great game, the first in a series of great games. Highly recommended!