I'm on the back end of Zarathustra at the moment, hence moving onto something a bit stronger. I tend to flick between different books by any given author in order to assimilate their ideas, so I might add Birth of Tragedy at the same time - thank for the recommendation. I'd like to get through all of Nietzsche's key writing in the next couple of years.

I've thought about reading Schopenhauer as I understand he's a great complement to Nietzsche's work - I'll see where I get to with Nietzsche first. Camus is somewhat related as an absurdist compared to Nietzsche/Schopenhauer's existentialism, but a bit more optimistic about the possibility of meaning.

I'm tempted to dig into Plato as the problem of universals is a philosophical topic that I value greatly, and his theory of forms is basically its origin story.