"A novel of alternate science among the crystalline spheres," as its subtitle proclaims, Celestial Matters is a work of alternate history, set in a world where the laws of physics are not those we understand today, but are those where the ancient Greeks where correct - and so are the ancient Chinese. In Richard Garfinkle's work, it is almost a thousand years since the founding of the Delian League, which is locked in war with the Middle Kingdom.

The novel follows Aias, scientific commander of the celestial ship Chandra's Tear, on its voyage out from Earth (the center of the universe) to Helios, where it is to carve a piece of celestial fire from the sun, which will be brought back to destroy the Chinese empire. Aias' mission is plagued by Middler attacks, whose weaponry is incomprehensible, as it is based on the principles of Xi.

Garfinkle explores this dichotomy of two sciences based on fundamentally incompatible principles, and the people who study them, with an entrancing style. His readers are assumed to have only a passing knowledge of the basis of the two sciences; Garfinkle explaining anything else on an as-needed basis.