Summary
Good game with a very disappointing last third.
The Good
I played many games and IT IS a good game...
The universe is original, it merges mechanic and magic, and the political context between the countries of Arcanum is an important side of scenario. In short the universe is very rich and well used.
The first 2/3 of the game are very very good. Even better than the famous Baldur Gate...
Important point : before starting the game, you can choose to play the official game OR to play games made by gamers or by even you (but not easy to make one). Then it's like if you play a whole new game in the Arcanum univers. There are a few ones on the Internet that you can download.
The Bad
Nothing except that an important thing looks obvious to me :
I think they finished to develop the game in a hurry and past the 2/3 of the game you can really feel it. Some important areas of the game that you heard of are small and not as great as announced in the game, some crucial movies are more slideshows than movies and the quality of the end is very disappointing. Too bad... because it could have been the best game I ever played without that.
The Bottom Line
The universe of Arcanum is so rich that I can only advice you to play this game. But be prepared to a decreasing quality on the end and maybe you will like the game as a great one.