The most salient theme in Cloud Cuckoo Land is that it is essential to preserve books and stories—and with them, the information they hold. Ensuring the survival of books and the knowledge they contain is an essential task in maintaining a connection across generations. Time and powerful entities are the natural enemies of books that eventually cause erasure of past ideas. As Licinius says to Anna during their reading lessons: A book contains the “soul” or essence of its author, who writes the book to preserve their thoughts, but “when a book goes out of the world, the memory dies a second death” (52).

Doerr’s book discusses many types of destruction as representations for erasure. Omeir and Anna, caught in the siege of Constantinople, illustrate the ways that war leads to the destruction of knowledge. As the Italian buyers explain to Anna, who does not yet understand the ramifications of the destruction of her city, “Permanence is only an illusion” (172). This theme is echoed in Trustyfriend’s forest because even though the forest sustained life for a long time, it is still destroyed. Rex offers another perspective regarding what happens when knowledge is snuffed out too early when he is discussing his Compendium of Lost Books: When only a fragment of a work survives, “it’s like the boys who died in Korea.