(get stories > return to london > find more stories)
This is really what it's about. More than leveling up, more than finding gear or a better ship or rare trade items, it's about this.
And you have to be able to enjoy said stories. FB and Alexis' ideas about storytelling are very formulaic once you've been exposed to it enough:
1. Introduce character as a broad generalization about who they are. Usually it's a juxtaposition of things that lend it quirky character. ("The Fearless Burser","The Withering Pirate","The Scrupulous Dockmaster","The Nervous Devil")
2. Drive the story forward with facts not in evidence. A lot of what stories are about in SS (and Fallen London) are things you as the player don't understand or know about. In some ways, it's like being part of a super esoteric conversation you aren't qualified to be part of, but are anyways. Furthermore the way that conversation is handled between the game, its characters and you, is the game and its characters speaking with a deep-seated understanding of what's going on. Hard details and explanations are rare. In fact they're the biggest prize in FB games. Where someone just actually explains what all these vague, disturbing allusions really mean.
Maybe you as a reader like that. Maybe it evokes your imagination, presents a world of impenetrable mystery. For some people the mystery is what really drives them, not the answers. In that sense Fallen London world is a pretty good one to get lost in. There IS a thread of coherency to it all. But I can only say that after years of playing Fallen London and about 70% of Sunless Sea. If you LIKE the search for esoteric knowledge, that's really what FB games are all about.
On the other hand, if you find the writing style annoying, or intentionally vague so it never really has to explain itself, if you find the whole conceit behind the writing without weight....FB games aren't for you. I find myself often on both sides of the fence. I both like what the world is about and how it's executed, but sometimes how it's executed is so incredibly contrived it's hard not to notice it.
3. Unhappy endings. FB isn't great about rewards. They're like that GM who thinks the real payout for players is the emotional impact of their stories, and for FB, that emotion is usually one of loss, betrayal, decay, fatalism, regret, Sophie's Choices, redemption and occasionally plucky, quirky, humorous themes to lighten the tone. So if you're not into the stories, from a mechanics standpoint, the game does not do a good job of rewarding you. Physical things and gear and progression are there ultimately to facilitate you seeing more stores or getting different results. For completionists, that often means walking face first into a horrible, tragic ending in SS with a so-so reward tacked on to the end so it's not PURELY a "well wasn't that horrible?" moment. It's usually a bad sign to me when a game is so committed to its story it literally has to put "Warning: Cliff Ahead" signs in bright red letters. That is not in any way an exaggeration about Sunless and FB games in general. They're the artsy White Wolf GM to your friendly neighborhood D&D Hack 'n Slash GM, trying to get player's in the Hack 'n Slash GM's neighborhood. If FB took themselves too seriously it would be too much. But they step back from that with the occasional humorous/quirky bits and the somewhat cutesy art style.
4. Mechanics just really aren't FB's thing. They grasp the fundamentals but their whole ideology of gameplay is built off FL, which is a check-in style web game. Most of the framework of the web game makes up the foundations of SS. Right down to the story structure being what you hang your hat on. Unfortunately the "congratulations here's a window pane of full of flavor text and a couple character quality changes as your reward" style of gameplay doesn't translate solidly for everyone to a video game where your ass is in the chair for hours playing it. FB's lack of experience with action and twitch gaming really shows in ship combat. It's fairly awkward and feels dangerous until you understand how it ticks, at which point it becomes predictable and boring. Even if you like the story side of SS, it's hard to rave about the mechanical side. It does its job of facilitating the story side but doesn't feel like it really ever rises above the web game.
All that said, I do enjoy the theme, the tone, the execution (for the most part.) I enjoy exploring the Zee, plying travel routes, managing supplies, trying to get those rare stories to pop. It's possible to get immersed and roleplay your ship's captain. Unfortunately the the "survival" part of the game dwindles as your knowledge increases, until it becomes about simply running the numbers from FL Port, in a big circle, and back again. The storylets are mechanically the only thing that can surprise you and they can only pull their tricks one or two times before they're filed away firmly in the "Been there/done that" drawer. When I think about playing SS again, my ideas of replay are like "Play as a Captain who pursues that one storylet where he dies/goes crazy/goes beyond the edge of time and space." The legacies exist so those playthroughs aren't purely about the story, but still. It takes a ton of busy work just to get a captain to that point.
And in the end, that's the biggest disincentive for me to play SS more than I do. It's just very time consuming game to get through, as the same FL grind gets applied to SS on a slightly larger time scale. (Or not. There's some stuff in FL I've been grinding for literally a year straight and still am not there.) That alone makes it hard game to come back and play a lot of the time, despite me liking it. You spend a lot of time grinding runs across known ports playing known storylets so you can get more echoes so you can buy one of the dozens of upgrades that will help you explore further and further out to Zee. You're really spending time grinding to facilitate the actual exploring and discovery, i.e. the best part of the game. That can become a tiresome cycle when you hit the mid game and want to buy the biggest ship, a zeeside mansion, all the best ship components, travel to the edge of the map, etc and so forth.