The Book of Stars is the Light conterpart to the Book of Moons. Few things are known about it, except that it has been in the possession of Xavier for a long time, as part of his collection of objects. It is unknown if there is a "trade" involved like the Book of Moons.
It is a black leather book like the Book of Moons with Niadic, an ancient Caster language, looped around the edges of the cover and a cluster of stars embossed in the center. The spine is presumably inscribed with symbols and languages like the others.