Apart from adding skills, stats and careers to a shooter, System Shock 2 features a number of ways to work your way around enemies instead of simply shooting them as the basic gameplay model would suggest. You can hack turrets to turn them to your side, you can use stealth and Psi abilities to bypass sticky situations and you will use your skills to great extent as your weapons need repair, items need to be researched and pieces need to be found to complete the puzzle of the story.
System Shock 2 has an amazingly deep and detailed story, revealed through audio logs of the deceased crew of the starships Von Braun and UNN Rickebakker, and by the main villain of the story. Though the game is the successor to the original System Shock, the basic plot of the original is explained in the prologue of System Shock 2. Playing the first game is not a requisite to enjoying System Shock 2.
One of the greatest innovations of System Shock 2 is the enemy AI. If your character is loud (for instance, opening doors, firing guns, dropping items) any enemies nearby will hear you and come running. This and a near-constant lack of ammunition force players to think tactically before rushing headlong into battle.