It is quite something that, while I think it is one of the most original and interesting game releases around, I have to recommend against it.
Sunless Sea, as a story to be unraveled and explored, it is fantastic. It packs a great amount of literary content (and I do mean by "literary" given how many words this has), solid worldbuilding and the constant feeling of "there is much more in the background", thanks to how the lore is revealed to you: snippets, fragments and bits that by themselves may seem quirky, odd or totally alien, but as you go around and learn, a bigger picture starts to form. Exploring the mysteries of the Neath and the Unterzee while avoiding whatever unknown terror of the depths, the dread of hunger, the lack of critical fuel or even the very wrath of strange gods is atmospheric
, to say the least.
If only this was an interactive fiction, though.
Sunless Sea, however, is a game. While story and ambience are clearly paramount in this, the "game" part is, well, not good enough. Since you need to engage with the game in order to explore the story, it suffers due to bad gameplay: once the novelty is gone, you will be instinctively drawn to keep your beaten old steamer around the familiar routes of Fallen London and try to grind some measure of resources to make sure you can survive your next journeys. Sunless Sea makes very clear, from the beginning, that it wants you to take chances and explore - but when you have lost a few captains and you are generally aware of how things work, you realize how woefully lacking is the earliest part of the game and how much of a slog it is to make a modicum of improvement.
(This doesn't get any better even after that.)
Which brings to the problem. The game's economy is focused on the three critical resources: hunger, fuel and terror. Managing all three may seem like a juggler's act, but a few tries here and there will give you the hang of things. Echoes, the currency proper, is the solution to the balancing act. You can afford a better engine, which makes journeys faster; better weapons, which makes you able to fight whatever the zee throws at you; a better ship, which makes everything more useful. Because of that, players quickly realize that they need cash early on to overcome the slog.
And, of course, you start to grind. Because you are grinding, you are not exploring. Because you are not exploring, the game loses its charm and effect FAST. But you need to cash in order to explore without being an awful drag. Of course, given how things work and the very orientation Failbetter wants for Sunless Sea, they quickly took care of the means to make money that were seen as "gamey" (see "The Sunlight Trade" if you are curious).
Sunless Sea is very original and has a lot of entertaining stuff, packed to the brim with lore of their setting (which comes from Fallen London) and the siren's call of a big, unknown Unterzee beckons and dares you to explore all of it. However, the sluggish, dragging-by-its-feet gameplay, an extremely repetitive early game (again: once the novelty wears off) that quickly becomes plain boring and a lack of alternative means to allow its players to just succeed
means that is not for everyone.