Far Sector by N. K. Jemisin

A Green Lantern dispatched to the farthest reaches of the Corps becomes a reluctant investigator when a string of violent deaths rocks a vast, technologically advanced metropolis whose peace is enforced by a data-driven system of social governance; as she navigates alien cultures, political factions, and the limits of her authority and power ring, the case forces her to confront thorny questions about justice, accountability, trauma, and what it means to belong in a society that quantifies conformity and dissent.

Purchase from Bookshop.org