u/BotWithFeelings1998

I recently tried finding similarities in the kind of literature I've been reading and liking - for eg The Wall by Marlen Haushofer, Orlanda by Jacqueline Harpman, the Woman Destroyed by Simone de Beauvoir etc. I noticed that most of my readings hint at an absence of a grand narrative and a rigorous investigation of just 'being in the world'. To be able to explore such literary pieces further, it would be better if I am able to categorize them somehow. I tried searching online and it linked the pieces to existentialist literature. How to know if a piece is existentialist or some other theory of philosophy is applicable? Is this categorization subjective?