The Last Kingdom. Iron Blood, #1

Azari is the last free city on the continent. For eleven years, General Kamau has held it against the Syndicate's expanding empire - not with armies, but with iron, with strategy, and with the ancient energy of the Iron Core buried beneath the city's mountain. Then the Syndicate sends Wanjiru: a field operative trained to dismantle exactly the kind of resistance Kamau has built. She is efficient, loyal, and very good at her job.
She is also beginning to understand that everything she was told about Azari is wrong. Iron Blood: The Last Kingdom is an Afrofuturist novel of war, defection, and the cost of standing at the edge of history.