Cloud Cuckoo Land by Anthony Doerr

Thirteen-year-old Anna, an orphan, lives inside the formidable walls of Constantinople in a house of women who make their living embroidering the robes of priests. Restless, insatiably curious, Anna learns to read, and in this ancient city, famous for its libraries, she finds a book, the story of Aethon, who longs to be turned into a bird so that he can fly to a utopian paradise in the sky. This she reads to her ailing sister as the walls of the only place she has known are bombarded in the great siege of Constantinople. Outside the walls is Omeir, a village boy, miles from home, conscripted with his beloved oxen into the invading army. His path and Anna’s will cross.

Five hundred years later, in a library in Idaho, octogenarian Zeno, who learned Greek as a prisoner of war, rehearses five children in a play adaptation of Aethon’s story, preserved against all odds through centuries. Tucked among the library shelves is a bomb, planted by a troubled, idealistic teenager, Seymour. This is another siege. And in a not-so-distant future, on the interstellar ship Argos, Konstance is alone in a vault, copying on scraps of sacking the story of Aethon, told to her by her father. She has never set foot on our planet.