Their stories are bound by an Ancient Greek codex entitled Cloud Cuckoo Land that each of the five characters discover and find solace in.

It is a fictional book written by real Greek novelist Antonius Diogenes in the second century, and tells the story of Aethon, a shepherd on a quest to find the fabled paradise in the sky.

In the fifteenth-century Byzantine Empire, Anna is an orphaned young girl living with her older sister Maria in Constantinople, where they work for a group of church seamstresses.

Anna secretly learns to read Greek and, with the help of a local boy, takes out old books from a tower to sell to Italian collectors.

Throughout the early 21st century, Seymour, a disturbed autistic youngster raised by a single mother, is attached to a wild owl that lives nearby and is increasingly dismayed by deforestation in Lakeport.

Seymour is arrested and spends the following decades performing prison labor for the Ilium Corporation, which is developing the Atlas, a virtual map of Earth.

Seymour is tasked with removing unsavory images from the Atlas, but eventually subverts this directive by hiding the true photographs of Earth's climate changed-induced decline under owl-themed items.

She learns that her great-grandmother was Rachel, one of the children saved by Zeno in the library, who had received a copy of the translation and passed Aethon's story on to Konstance's father.

Doerr stated in Cloud Cuckoo Land's "Author's Note" that his novel draws on several other books, most notably Antonius Diogenes' now-lost "globetrotting tale", Wonders Beyond Thule.

[9][10] Publishers Weekly, in its starred review, wrote, "Doerr seamlessly shuffles each of these narratives in vignettes that keep the action in full flow and the reader turning the pages.

[12] In a review in The Guardian, Elizabeth Knox called Cloud Cuckoo Land "a gift of a novel", that is "large-hearted ... joyous [and] a deep lungful of fresh air".

[3] In another review in The Guardian, Hephzibah Anderson wrote that Cloud Cuckoo Land is full of "[w]onderment and despair, love and destruction and hope".

[13] Marcel Theroux wrote in a review in The New York Times that Cloud Cuckoo Land is "a wildly inventive novel that teems with life, straddles an enormous range of experience and learning, and embodies the storytelling gifts that it celebrates.

[14] He said that while the sections in the present have some of the novel's "strongest plotting and best writing", the Constantinople pieces tend to stagnate, and the time spent aboard the Argos "reads like a literary fiction author attempting to do sci-fi".

[14] Pierce concluded that overall, the novel's plot is "technically, masterfully done", and notwithstanding the weaker sections, it keeps moving at a brisk pace, but added that "there may actually be some truth behind the concept of something being too big to fail.

[15] He wrote that while each character's tales could have been a captivating novel (barring the science-fiction story, which he said "has a moldy Twilight Zone funk"), Doerr slices the plots up and scrambles them, creating "a textual puzzle as complicated as the ancient Diogenes codex.