The protagonist, Hanna, is sixteen, manic depressive (and explicitly, canonically prefers that descriptor to "bipolar", Because Reasons), and Finnish-"island girl" (Hawaiian?), raised (for most of her life) in Dallas. She describes herself as biracial and bicultural, and she's bilingual in English and Finnish - and the codeswitching is genuinely plausibly represented.
The dude she ends up hanging around with a lot is the same age, Latino, and bilingual in Spanish and English - again, really nicely represented.
The story takes place in creepy smalltown Texas. It's sub/urban fantasy and abusive parents and a critique of the medical-industrial complex and teenagers having (complicated, not always happy) sex lives all tied up in tight, funny monster-killing brilliance. It's lovely.
( Content notes. )