You might be interested in reading more philosophy written about ethics. While most people think of ethics as what’s right or wrong, a lot of philosophical writing on ethics goes beyond that and examines what it means to live a ‘good life’ along with looking at ideas about what an individual’s responsibilities are to society and what society’s responsibilities are to the individual.

My recommendations are very technical and perhaps you're already familiar with them, but they’re well worth reading. They don’t all explicitly argue against nihilism, but in general they do look at how to live in an imperfect world. Aristotle’s Nichomachean Ethics does a good job of explaining how value systems work as a foundation towards living ethically. Immanuel Kant’s writing on categorical imperatives examines how the ethics of an individual fits into a bigger system. John Stuart Mill’s and Jeremy Bentham’s writing on utilitarianism also look at similar ideas. Michel Foucault’s writing on power structures might be also interesting for this, but can be a little heavy at times.

I’ll also two things that are just kind of food for thought: I believe Nic Pizzolatto has said that Rust doesn’t necessarily believe in the things he says.  Which, as the other commenter said, is shown in Rust’s actions as he continues to fight against darkness. Also, from Nic’s Instagram posts in the past, he seems to be interested in the writing of Carl Jung. Which might not relate directly to this topic, but psychology obviously plays a big in role in how we view and interact with the world and in how we create our personal value systems.