The last game in the Zero Escape trilogy, Zero Time Dilemma, has finally been released and long story short, it's great. Since it's the third game in the series, it's really important that you played the first two games as the third game as you would expect, continues the story from those games but also features characters from the first and second game as well. .
Unfortunately the first game in the series, 999 is a little difficult to come by since it was only released for the DS and the iOS port, which I dont recommend, removed all of the room escape mechanics and was pretty much an abridged version of the game.
At Anime Expo however, Spike Chunsoft announced that both 999 and Virtues Last Reward would be getting ports to other systems, which I am excited for because it means that more people can enjoy these fantastic games. I enjoyed 999 so much, I even named it my #1 game of the last generation of gaming.
The ports are currently "in progress" and there is no word yet on what consoles each game will be available for.
If I had to guess though, I would think that 999 would be ported to the 3DS, Vita and PC with Virtue's Last Reward getting a port to the PC. That's just speculation on my part so don't read into that too much.