I'll definitely be grabbing this one tonight. Based on the little time I've spent with the web version, this will be a great one to explore.
I've played a good bit of Sunless Sea. It is one of my favorite indie titles on Steam in recent years. It takes the atmosphere and writing skill of Fallen London and adds a somewhat action-based RPG along with it. I say somewhat, because while you do steer a ship around, other than some real-time combat - which moves pretty slowly for an arcade game - there isn't a lot of the kind of action you would find in the typical action-based game. The "action" part is really just a way of moving through the world for the most part.
I REALLY hope they eventually port Sunless Sea to iOS. In the meantime, we have Fallen London and Sunless Sea is playable on Windows and Mac OS X.