Right now I'm trying to write a book with a sort of dark theme or undertone to it. I want to make the words themselves beautiful while still portraying the characters as who they are- Eugene, the quiet, optimistic girl who's falling in love with the new kid from California, and Jupiter, her cigarette smoking best friend who hates pretty much everyone. Its hard to convey beautiful writing without giving a romantic undertone, and Eugene and Jupiter definitely aren't in love. HELP!
I'm not an expert by any means, but the first thought that popped into my head is maybe read through some romance books with the 'pretty' writing and see what kind of adjectives are common.
I feel like the story you are describing is almost like a John Green book, but without the romance aspect of it. Where it gives off a really real teenage like feeling. I think it is really easy to write about romance, but I also think that writing can still be beautiful without romance involved. Maybe you can try to write the story with a more poetic vibe. You can still keep the basis of your story but maybe try to write a bit about the scenery or the feelings of places throughout the story to give it poetic descriptive wording, without making it too romantic.
a great way to cancel out romantic feelings between Jupiter and Eugene: give Jupiter a romantic partner
Describe sensory details more than emotional, and use upbeat tone, syntax and diction to do so. I often find that portraying something with a detached elegance helps portray the "pretty" while leaving out the romantic.