https://itunes.apple.com/jp/app/steins-gate/id454136236?mt=8
https://play.google.com/store/apps/details?id=com.mages.stei...
I got into it because I wanted a break from more traditional games (such as RPGs) which may claim to have a story but often don't go deep into character development and so on. If that's what you want, Steins;Gate definitely delivers.
I'd make two cautionary points if you're going to try it:
1. It's a visual novel, so it's not going to be interactive like a more traditional game. You get some choices, which among other things determine what ending you get, but really don't influence much otherwise.
2. There's a lot of banter. You'll know in the first 10 minutes of the game if this bothers you or not. I personally didn't have a problem with it, but your mileage may vary.
If you're not sure about reading it, the anime is also really good. It's obviously much less detailed than the visual novel (compressing ~40 hours of visual novel into TV format is hard) and omits some sizable plot points, but it's still great. The first half is fairly slow set up before it hits like a truck.
An English version of the game is now up on Steam. Highly recommended. http://store.steampowered.com/app/412830/
[1]: Edit: the game. Not sure about the anime.
[2]: Edit: In the game at least this is more in depth than just a password. Saying more would require spoilers.