This is the second book in the Teixcalaan series by Arkady Martine and follows a few months after the prior, A Memory of Empire. Here is the Goodreads blurb:
An alien armada lurks on the edges of Teixcalaanli space. No one can communicate with it, no one can destroy it, and Fleet Captain Nine Hibiscus is running out of options.
In a desperate attempt at diplomacy with the mysterious invaders, the fleet captain has sent for a diplomatic envoy. Now Mahit Dzmare and Three Seagrass—still reeling from the recent upheaval in the Empire—face the impossible task of trying to communicate with a hostile entity.
Whether they succeed or fail could change the fate of Teixcalaan forever.
Read on for my spoiler-free review.