The classic story of first contact.
It situates us in the difficulties of the rising Second Empire, reuniting mankind after the Secession Wars, with Roderick Blaine's position in the navy. He's promoted to captain to take the ship he had served back to a planet for repairs after battle (with a few passengers added, not entirely convincingly), and is there when an alien ship -- the first aliens humanity has learned of -- arrives, and he has to intercept.
The pilot dies. And they conclude where it came from, and that they have to investigate.
There, they find the Moties. And the rest of the story revolves about learning about each other and whether and how they can co-exist. Confusion, misunderstandings, and willful secrets and deception. It includes a zoo, tales of brownies, a funeral where the salute disintegrates the bodies, Moties' legendary figure Crazy Eddie -- a noble idealist always doing disastrous things, an icon on the ship <I>Lenin</I>, the Moties' genetic castes, Plato's <I>Republic</I>, and more The Moties are in many respects like humanity, making some things all the more tragic.