An incredibly mixed bag. Its very deep stat system and occasionally interesting challenge areas and boss fights are quite good, but ultimately these highlights are overcome by extreme linearity, way too many trash mobs, next to no plot, and one of the worst cases of hitpoint bloat I have ever seen in a game (late game there are some random enemies with 4,000 hitpoints. Given that the average character can do 50-100 points of damage per turn, you can work out the problem here). I really love spiderweb games, so I hate to bash this, but this is probably their worst.
Of couse I still forced myself to finish the whole thing on torment difficulty, but that's only because I'm a total OCD, power gaming, masochist (and for all the game's faults, it is refreshingly difficult). Normal people who demand things like "enjoyment" and "entertainment" from their video games (novel concepts, I know) need not apply. Or better yet just play one of the other Avernum games (most of which are way better).