Theseus calls for his master of ceremonies to inform him what entertainments are available for them as a part of wedding feast activities. Philostrate, the master of ceremonies, first offers a story about a battle between Centaurs. This is to be performed by an Athenian eunuch, accompanying himself on the harp.
Theseus says that he has already told this story to his bride-to-be, when he was giving her details about one of his relatives
If the "books" wasn't a plural, it would be "his" but since it isn't singular, it would be "their"
A. It gives readers a sense of grasping for something that can't be caught.
We can't help you without you telling us the whole story or giving us a link to it, we have no context.