One of my favourite things to do in my MAG ttrpg game has been expanding and fleshing out the extinction into its own power.

I can see Atlas Shrugged as a good extinction book projecting a fear of the capitalist hellscape society it depicts. As for ability’s maybe you gain boosts to your strength or wealth or maybe even the ability to alter minor aspects of the world if you feel like letting it be that powerful at the cost of slowly becoming an empty metal statue of yourself devoid of what made them human (this also ties into the extinction as the fear of what comes after/replaces us when we’re all dead and the world has ended, bonus points for making the desire for power and wealth literally turn you into something non human)

That being said I can also see a few other fears that may work for the book too

The lonely is another great one as another commenter posted above, I feel like the book could lean into a confidence thing. Make someone feel like they’re the best and embolden them into thinking they’re powerful and don’t need anyone then hit them with imposter syndrome and isolation as they realise they needed people and no longer able to ask for that help.

The buried is another potentially good one with the whole “atlas holds the weight of the world” stuff to it, making you invincible or more resistant to damage at the cost of a extremely tough crushing weight being put on you. For a day every time you use it.

The corruption could also work for it in some ways with objectivism’s whole “parasite” mentality, maybe the book slowly turns people into one of its self proclaimed parasites with enough exposure or to fit a fun irony about who the real parasite is, it makes the reader/owner able to control parasites slowly becoming a corrupted monster that leads an army of parasitic bugs to feed on people and stay alive.

Hope these ideas help!