Thief: TDP is an awesome stealth game with and interesting story.
The game's graphics definitely don't look amazing today but I'm sure they were pretty decent when the game came out in 1998. The sound in the game is of course very good, it has to be good to be a successful stealth game. Some sounds like the swinging of your sword sound a little unrealistic but those don't really matter. The sounds that help you detect if someone is coming matter. The footsteps, the sound of the type of floor the feet are stepping on and doors opening and closing are the very important and useful sounds. For example, you’re looking for valuable items in a room and suddenly you hear the door open and foot steps walking in onto the rug in the middle of the room, letting you know that he’s right behind you. Almost all guards mumble and complain about stuff while patrolling and guarding, normally making them easy to hear before turning a corner or running into the light in case you didn't see them. The voice acting in the game is absolutely perfect, from the hilarious drunk or stupid guard to the screaming beasts, the voice acting is perfect. Oh and Garrett's voice acting is pretty good to.
The game doesn't always take place in a heavily guarded mansion but that's all I'm saying. The story is good and interesting, I didn't fully understand until I played Thief III because it introduces the factions pretty well, unlike this one where I never understood those quoting intros. The weird thing about Thief is that there's a faction called Hammerites, these guys are religious mechanist who have steam powered machines that didn't exist in that time. Someone on the TTLG forums called me an idiot and told me it was called something like "Steampunk".
I highly recommend this game to anyone who enjoys stealth games. It's definitely one of my favorite games ever. Play this game.