God. Where to start.
Since on the whole I adore this game, I'll start with my problems with it, to be absolutely fair.
My biggest, most serious issue is that the game is INCREDIBLY GRINDY. Incredibly grindy, and you can die very easily and lose all that progress. I understand that a small ship wouldn't reasonably do very good business trying to transport goods, but for god's sake, I should be able to make more than a $1 profit on anything I buy to sell (if that!). Either that, or you should have the option to pass on your ship to your progeny, and they can keep the money they would otherwise spend on that ship. As for how easy it is to die; once an enemy has you up to nearly full visibility, it's nearly impossible to get back down to a level where you can safely attack. From there it's just a matter of time before it tears your crew apart.
The other issue I take is that you can run out of fuel close to a port but not docked in it and have to lose the game that way. Surely, you could hire someone to come tow your ship (and if you're out of money, THEN you're dead). Perhaps only certain ports can tow ships. Something. Perhaps you could abandon ship into a small rowing vessal, attempt to get to port, and then from there perhaps have to owe somebody something. The most frustrating defeats I've suffered have been floating uselessly while touching shore. Very. Frustrating.
I would also add that this game is rather poorly tutorialized. It tells you what you need, but it won't give you any real tips or guidance about the safest way to navigate the zee, given that you only have so much fuel and so much food. An early run isn't going to last very long because it's nearly impossible to know just where you need to go and when, and then any grinding done is lost.
However, I only say these things because I love the game, and I wouldn't want to give someone any false hopes. God knows the zee would only crush them.
If you're not scared off yet, though, there is a sort of ruthlessness to the game that makes me want to beat it into submission. Coupled with a haunting atmosphere and horrors that are very effective at knowing the line between "unnerving" and "over-the-top-cheesy", Sunless Sea is genuinely a game that intimidates me. I get chills when I have to leave port, since there is a very deep uncertainty that I'll ever be returning. The art is incredible, the music is catchy (and at times gives me the same fright I get at the Sonic drowning music), and the writing is well worth crossing the seven seas for.
Long story short, if you bore easily but are very into Lovecraftian horror, wait for a sale. If you're willing to put in long, hard, heartbreaking hours for a game that will sometimes honor you with a very delicious crumb from time to time, welcome aboard.