It seems to me that it is a historical economic sim, and one with a great original concept at that. Surprised that there haven't been more slave-trading games, personally.
...why? I mean, slavery is
just a commodity. A commodity with specific problems attached (trying to acquire slaves in the first place by selling guns to African slave traders, transporting them by boat in a manner that doesn't lead to most of the slaves dying off, defending yourself against slave mutinies), but at the end of the day, the best way to get rich is to buy low (in Africa) and sell high (plantations). It'll be just a dressed up Tradewinds...
...at least until the abolitionist movement kicks in. At first, they'd outlaw the slave trade, but that'd fine, you'd smuggle them into the country. Then the abolitionists move towards weaning society off slavery or outright outlaw its practice, driving the slave market completely underground and forcing you to take more and more risks to sell your wares. And then when European imperialists march into Africa to subjugate those backwards tribes (under the premise of "ending the barbaric practice of slavery that
us enlightened Europeans abandoned
"), the supply of slaves will begin to dry up. And considering
how slavery still exists today, there's lots of room for expansion. The goal of the game is not to become the "most powerful slavetrader"*...but to be the "last standing slavetrader" as the entire world rallies against you.
*By the way, this rhetoric from the trailer makes me think that this is a MafiaWars clone.