Calderón, Emilio. The Creator's Map (New York: Penguin, 2008) 259 p. Originally published in Spanish as El Mapa del Creador (Barcelona: Roca, 2006) translated by Katherine Silver.

In 1937 the Spanish Academy in Rome is being run by the secretary of the Spanish embassy. Secretary Olarra is a graduate of the Vatican School of Library Science, but he neglects the Spanish Academy library in order to concentrate on translating the Vatican Library cataloging rules into Spanish. The Academy students sell off valuable books from the library to raise money. One of these students, Montserrat (called “Montse”) is later hired as a librarian at the Palazzo Corsini. Father Giordano Sansovino is a librarian at the Vatican Library. He explains a problem with the library.

...the library contains more than a million and a half volumes, a hundred fifty thousand manuscripts, as many maps, and sixty thousand codices in about thirty collections. Out of all of that, we know the contents of only about five thousand, even though we've been cataloging since 1902. One person cannot catalog more than ten a year. It takes a long time to read, check, systemize their contents, so it will be another century before we can know what is really hiding in the Vatican Library. (p. 80).

This is why the library is the perfect place to hide documents.