Yes, it will deviate from those RPG tropes. At least, the main plot will. It has lots of cool twists and turns that I didn't expect... it starts with standard fantasy fare and then changes things up as you get farther. I think the main plot is one of the best in any RPG I've played.
But the main way that Arcanum differs from other RPGs is the way it reacts to your choices. There are usually many different ways to solve every quest, and people's reactions and even the outcome of some major events will depend on what you do. A lot of this won't be evident on your first playthrough, but if you come back and try different characters who play differently and make different choices, you will really see how well the game adapts to the player. And I highly recommend trying out different characters; it's one of the best parts of the game.
One word of warning: it sounds like you're in Tarant at the moment. The next step in the main plot can be very aggravating. You should probably spend some time doing side quests (check out some other cities too) before tackling it, and when you do tackle it, try to be patient and persevere. It's probably the most annoying part of the game, but it's also the point when things start to get interesting.
That is good to hear then. I do not feel the need to hurry up with the main plot, as I enjoy playing RPGs mostly for varied side quests and C&C (if there`s any), and I read that Arcanum was strong in these, however the side quests I picked up so far just seemed very generic. Guess I`ll just have to look for more.
Actually, I have already tried several characters to see which one would suit me best for a first playthrough, and I have settled for a halfling specialised in throwing, lockpicking, some tech, and just a little bit of diplomacy. ( I`ll try to focus on only a few of these though, so as not to get a jack-of-all-trades-but-master-of-none character, as these do not seem to survive too long in this game.)
I also tried playing with a black necro specialised mage, but I was dissapointed in the fact that while negotiating with the necromancers under Tarant my character did not have dialogue options which would reflect her obvious knowledge in the "darker arts", and had to act like she was not conversing with corpses on a daily basis. Fights were a cakewalk with her though.