Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Lonely and Meditative
The narrator of this book is the new kid on a ship full of men who've known each other a long time (not to mention he's the captain), so it's understandable that his tone would contain its fair share of loneliness. On top of that, the tone also shows us that the captain does a lot of thinking. What else are you going to do out at sea with no friends to talk to? The narrator sets his tone early on, telling us in the story's seventh paragraph:
All these people [my crew] had been together for eighteen months or so, and my position was that of the only stranger on board. I mention this because it has some bearing on what is to follow. (1.7)
In other words, he's lonely and he wants us to know it, because it will color our reading of everything that comes after…like why the captain chooses to protect a murderer for no apparent reason.