System Shock 2 is a cyberpunk RPG/Shooter hybrid with an emphasis on exploration and resource management. Just like its predecessor, it makes ample use of audio logs and e-mails to tell the story and requires memorizing a fair amount of keyboard shortcuts.
Also, while I think the audio logs are cool, the story is nothing special. I mean the big plot twist is spoiled by the box cover.
The game is also famous for its atmosphere and sound design, both of which are indeed fantastic. I think System Shock 1 had a better OST overall, but that's a matter of personal opinion. The constant buzzing of machinery combined with distant grunts make for a rather tense experience, all the enemies can be identified by sound cues alone.
Gameplay wise, System Shock 2 is a bit unbalanced, but that's part of the appeal, very few games allow you to be the invisible rocket launcher cyborg man. However, you should skim through the manual that comes with the game at the very least because it's possible to get stuck if you choose your upgrades poorly.
To conclude, I think System Shock 2 is a good introduction to the immersive sim genre and I would recommend it to anyone who likes very atmospheric games, cyberpunk (the genre, not the game) and RPGs in general.