To add on to what people have said about Age of Decadence: AoD is basically designed around two ideas--choice and consequence, and challenging turn-based combat. It is possible to entirely avoid combat (in fact, I'd recommend avoiding it as much as possible when you're new to the game unless you like dying a lot), especially if you play as, say, a merchant. The choice and consequence is what initially attracted me to the game, though I ended up enjoying the combat, too, once I got the hang of it and learned to min-max.
What is unique about Age of Decadence is that you play one of eight roles in an interlocking storyline, and you can play each of these eight roles in a variety of ways, and even switch factions midstream to enter into another role's storyline. It requires real intelligence and work to make the best decisions, since you not only have to choose the skills that will allow you to succeed, but you also have to figure out who is lying to you, cheating you, or otherwise misusing you. The opening town, for example, features a girl being threatened by a soldier. If you help the girl, you'll find out your purse is missing. If you realize what she's up to and demand her money instead, she'll lead you into an ambush. You can also play dirty tricks on your opponents, of course, particularly if you play as a grifter. Depending on your choices, wars can be won and lost, a city destroyed, leaders deposed, and so forth.
The game does have flaws, including an ending that's not quite as good as what comes before, but what it offers is fairly unique.