Aye indeed, Planescape Torment is a masterpiece of digital art/literature fusion. It asks some big questions to the player whilst sucking one's mind into a uniquely deep world, filled with fascinating mini-stories and NPCs. It took me a long time last year to complete it and still it felt like many parts of it were unexplored. Utterly reccomended for players who want more depth in their games.
I managed to buy it from a local second hand store for $15 AUS, although it did come lacking the proverbial RPGers map which I've still yet to find someone willing to part with .
But yeah, may your quest to find it be successful!