In the early 16th century, Hernando Colon, the bastard son of Christopher Columbus, set about collecting the largest and most comprehensive library in the western world, funded by his father’s pillaged New World wealth. Though Colon never did manage to collect every book in the world—an impossibility given the proliferation of inexpensive printing technologies—he was able to gather more than 15,000 hugely various volumes, covering popular as well as academic subjects.

More impressive even than his collection was the cataloging scheme he devised in order to make the huge number of items—books, pamphlets, letters, and manuscripts—navigable. At his employ, hundreds of scribes trawled the stacks, summarizing works and labeling works according to Colons hieroglyphic system. All of this went into the massively ambitious Libro de los Epítomes: The Book of Summation. This more than 2,000-page long volume was an incredible window into the collective literary life of the 16th century, especially valuable since many of the books it cataloged no longer exist in any form. Unfortunately, the Libro de los Epítomes was lost for more than 350 years, along with 75% of Colon’s library.

But, in 2013, Guy Lazure, a historian at the University of Windsor in Ontario, Canada, found himself in Copenhagen, researching the collection of Árni Magnússon, a 17th century Scandinavian scholar, whose collection included a small number of Spanish texts. Lazure, an expert on the history of Seville, had been invited to examine the Spanish collection, and found among them a peculiar, untitled, unattributed, and extremely large volume. Colon’s unique cataloging system was immediately recognizable to Lazure, and in short order, he realized he had discovered the sole surviving copy of the Libro de Los Epitomes.

Ironically, Lazure’s discovery itself went unnoticed for several years until Dr. Edward Wilson-Lee published a biography of Colon, The Catalogue of Shipwrecked Books. Speaking to Marco Werman of Public Radio International, Wilson-Lee summarizes the import of the volume, and of Hernando’s library:

The library at Hernando’s death was 15,000 to 20,000 volumes and they only summarized 3,500 of them. This manuscript is not complete, so there’s a little over 2,000 books summarized in this. But, very excitingly, many of these books will probably not survive anywhere else in the world in any other form, so this is a catalog of lost books in a really exciting way. It is a gorgeous thing.

Alison Flood, writing at the Guardian, reports that Wilson-Lee and a collaborator are working to digitize the contents of the Libro de los Epitomes, and to publish a complete account of the library it documents.