Myst is an interesting game, especially in light of the effect it had on the games industry when it was released. At the time there was literally no other game like it, and it tended to polarize gamers who either loved it or derided it as not even really being a game, but just a slideshow that you clicked on. In my opinion, some of the "copycat" games that built on the style of Myst were better games (but a lot of them were really bad), but I also never played Riven or any other sequel so I can't speak to those.
The thing I liked most about Myst was the imagination put into its environments. There's almost a light steampunk vibe to the design of the various areas, and I really liked the sense of atmosphere given to each area... there is very little explanation for why these strange structures are here, they just are. I thought that minimalist style worked really well for Myst, but unfortunately it also left the player with little in the way of direction. There is an area in the game where the player can receive hints about how to proceed, but the player never needs to find these hints and on my first playthrough I didn't, so I was basically wandering around at random, poking randomly at things with no idea of what I was supposed to be doing until I checked a walkthrough. The puzzles themselves are also rather strange, which fits with the style of the environments but also makes them tough to solve on one's own.
To be fair, I was younger at the time and might have had more luck figuring things out on my own if I played it for the first time today. But overall I think it's far more interesting as a milestone in gaming history than as a game in itself. It's probably worth checking out at GOG's price if you've never tried it before.