I've been playing this on and off for quite a while now, and I'm still in two minds about it. The premise is very promising, but, for me at least, the motivation fizzles out after a few sessions, although after a few weeks I tend to come back to it again.
The whole game is very story- and atmosphere driven, and its emphasis lies with the narrative. There's tons of reading to do. Think Planescape Torment here. The exploration is mainly a vehicle for exposition by the ton. And it's really good.
Then the menus. Oh Christ, the menus! They lead you around in circles, and you can find identical menu points in separate menus that are displayed on the main screen SIMULTANEOUSLY! It's very frustrating while you're trying to find your feet with the game, but you get used to it, although it remains an annoyance. There's enough to read without having such multiples hanging about. It beats me, why this hasn’t been eliminated yet.
Apart from that: you have to remember that at first your ship and crew are very weak. Stick to patrolling the eastern coast and don't venture into the open water, otherwise you'll die very quickly. Even if you do and have to start again, you get to pick one quirk from the previous game, so you don't start completely from scratch.
A tip: collect reports for the admiralty, and remember, you can visit a place several times and get a report every time. Many people apparently didn't know this; me having been one of them.
It's a game that always hovers on the brink of being deleted from my hard drive, but only ever just manages to scrape through. I've yet to play the Zubmariner expansion, but it's a good reason to give it another shot.