Carnival by Elizabeth BearRead about the other entries on the list.
Bear’s super spy SF novel begins with two operatives reuniting after many years to deliver a shipment of stolen artwork to a matriarchal colony planet after years of diplomatic tension—but really they are there to get intelligence for old earth’s government. Don’t walk into this book expecting good vs. evil or any simple, reductive morality—everyone possesses virtues beside their flaws. Come for the art reclamation, stay for the culture building, which won’t be anything like you expect.
--Marshal Zeringue