Just finished a reread and the character work still hits hard. Aza Holmes is the center, a teenager with severe obsessive-compulsive thoughts, and John Green writes her internal spirals with terrifying accuracy. It's less about what she does and more about the constant war inside her head.
Her best friend Daisy Ramirez is the brilliant, fanfic-writing counterbalance, all chaotic energy and big dreams. Davis Pickett is the billionaire's son Aza reconnects with, but he's defined by his own grief and loneliness, not his wealth. Then there's Daisy's boyfriend Mychal, the artist, who feels almost like a background note but adds to the group's dynamic.
What's fascinating is how Aza's mom and her therapist, Dr. Singh, are crucial too—they're the steady, often frustrated, anchors trying to hold her to reality. The characters aren't really 'solving' a mystery; they're all just trying to survive being themselves.