[Writing this an hour and a half before my Chiefs play the Eagles in the Super Bowl - not sure how thorough this will be!]
Long book. It's well over 400 dense pages; I'd say I put at least 20 hours into reading it, perhaps far more. Course this is par for the course for Conrad I seem to understand.
I read this book because I love the Alien franchise started by Ridley Scott, and he names the ship from the first film the "Nostromo". I decided after watching Alien for the umpteenth time that I wanted to see why he made this reference. Here are my surmises:
Betrayal, yes, there is a level of betrayal. The character, Nostromo, is a "man of the people" but a man who leads men, renowned for the control he exerts over his shipyard workers (the "cargadores"), his courage in skirmishes and entering hostile territory, and his faithfulness to his tasks. The biggest task in which he demonstrates his faithfulness is securing the safety of a huge amount of silver from the local mine. What's interesting is that he does this, at first, out of his loyalty to the rich foreigners in town who entrust him with the task as much as for the sake of his own reputation, to continue to be known as a man who gets the job done. But then, when the silver is "lost" by all accounts - just fortunately not into the hands of the enemy rival political party - Nostromo continues to hide the silver because it has come to claim his soul: he cannot part with this treasure forgotten to all world but him, and he becomes its slave. So this would be a major way in which Nostromo is so to speak "betrayed": that which he sacrificed his own health and safety to protect, ends up dangling before him a future of security and marriage and prosperity before it causes his own demise in his attempts to claim it.
Likewise, the crew of the Nostromo in Alien are bringing back a treasure of thousands of tons of some ore from deep space when they are redirected to inspect a signal coming from the planet LV-426. There is some talk that they might ignore that signal, but a "company man" reminds them that in so doing under company contract they could forfeit all their profits from the expedition. Thus they are obliged to take this side trip, a trip which ends up bringing the Xenomorph aboard and resulting in the deaths of the whole crew apart from Ripley (Sigourney Weaver's character). You could argue about some similarities here - Conrad's Nostromo "loses" the silver when in reality he stowed it away where only he knew; Scott's Ripley self-destructs the ship with all its mined ore, but manages to bring the true "treasure", in the eyes of the company - the Xenomorph, onto the escape ship with her. At the end of Conrad's Nostromo, technically the silver remains but it is ambiguous whether anyone truly knows exactly where it is and at the end of "Alien" the Xenomorph, this amazing specimen which seems it can survive the vacuum of space and without sustenance, is left floating in the dark, perhaps to be found some day far far in the future.
Oof. Gotta get to my Super Bowl party here.
To wrap up, it's not Just betrayal though that leads to Nostromo's demise. His own avarice and carelessness played equal parts toward his death. And that certainly is a theme in Alien as well. While the Company had moving parts seen and unseen to successfully retrieve this biological marvel from LV-426, a lot of poor decisions also led to the crew's demise. Haste, without which they might have decoded the signal as the warning signal it was rather than as a distress call. Undue curiousity, without which Kane might not have been infected. Ignoring protocol, without which the Xenomorph might never have come aboard. It seems a theme for both pieces of art is that, in the end, for the tragic figure, it is both fate or betrayal and one's own vices that synthesize to weave a tapestry of the hero's destruction.
May that not be the case for my Chiefs today!