Lavinia, daughter of the king of the Latins of Laurentum, is sought after by neighbouring kings, but knows she is destined to marry a stranger. This is Aeneas from the Trojan War, who arrives with a large body of Trojans. An agreement is made but then breaks down and there is war, which is won by the outnumbered Trojans. They found a new city called Lavinium, but Aeneas is killed after three years. Aeneas's elder son Ascanius founds Alba Longa and marries but fails to produce an heir. Lavinia removes her son Silvius from his control and he eventually becomes king of the Latins. Rome already exists, but as a small settlement that plays no part in events. Lavinia herself retreats from the world and at the end seems to have turned into an owl. She has all along regarded the world she lives in as unreal, a product of Virgil's imagination.
Background
The book is based on the last six books, or the Iliadic half, of the Aeneid. Throughout the novel, Lavinia holds conversations with "the poet," the shade of a dying Virgil. In this way, the novel forms a relationship to the original it adapts in the matters of its plot and through the ways that Lavinia's character relates to the poet and his poem. It seems Lavinia only exists in the context of the poem, and through her conversations with the poet, she is self-aware of her own textuality. This novel is not meant to be history. Le Guin says that "The Trojan War was probably fought in the thirteenth century BC; Rome was founded, possibly, in the eighth, though there is no proper history of it for centuries after that. That Priam's nephew Aeneas of Troy had anything at all to do with the founding of Rome is pure legend, a good deal of it invented by Virgil himself". She also explains that her work is a translation of the last six books of the Aeneid into prose. Le Guin's thinking about Lavinia as a translation demonstrates that Le Guin has a nuanced theory of translation. She adds much to Virgil's epic poem, but carries across much of Virgil's poetry and the world of the Aeneid in doing so.