A Classic Game in league with Ultima Underworld I and II
And why wouldn't it be in the same league? Looking Glass Studios was responsible for UU1 and UU2! This game is well thought out.
There are three main things that make this game great:
1. Story - The backstory is unlike any other in RPG gaming. You start on CITADEL, and you are the only living being on board. Everyone else is dead. You find out the backstory through the journals and datacards left by the dead residents of the space station. By the time the game is over you will have pieced together, bit by bit, the events leading up to the time you awoke (the start of the game).
2. Configurability (if that isn't a word, it is now) - The fact that the player can configure the game to his or her tastes is a great feature. Combat, Missions, Puzzles, and Cyberspace could be made as easy or as tough as you want. Like hard puzzles, but don't like strong enemies? You can set it with System Shock
3. Sound - One word: Eerie. Along the same lines a Dungeon Master and Ultima Underworld, the ambient sounds are well placed, and very creepy. Not overbearing, but not so soft that you can't hear them. Just the right mix.
The graphics are very dark, making it difficult (for me at least) to discern the end of a wall, etc.
The Bottom Line
If you like a very flexible game system, combined with the graphical feel of Ultima Underworld I and II, and sci-fi setting, grab System Shock. It's difficult to find, but you'll enjoy every minute.