The Codex Calixtinus, also known as the Codex Compostellus, is the main source for the 12th-century manuscript Liber Sancti Jacobi –Latin for “Book of Saint James”. This work is the first comprehensive guide for pilgrims traveling to the shrine of Saint James the Great in Santiago de Compostela. It includes sermons, miracle accounts, liturgical texts, descriptions of the pilgrimage route itself, and even polyphonic musical pieces. It offers invaluable insights into the art, culture, and customs of medieval pilgrims.
The Codex was put together before 1173 –most likely between the late 1130s and early 1140s, according to most scholars. It was probably written by Aymeric Picaud. The five books of the Codex are prefaced with a letter that’s been (wrongly) attributed to Pope Calixtus II. The appendix includes a letter by another Pope –Innocent II.
A “pilgrimage encyclopedia”

The texts in the Codex have a complex history. Each one of the books comprising the Codex probably existed before being put together in this “pilgrimage encyclopedia.” The Codex highlights Saint James as a patron saint in the fight against Islam in the Iberian Peninsula and has been suggested to even serve as a grammar book: it is deliberately written in poor Latin.
The oldest known copy was made in 1173 by a monk called Arnaldo de Monte and is preserved at the famed monastery of Santa Maria de Ripoll, in Catalonia. It was rediscovered in 1886 by Jesuit scholar Padre Fidel Fita. The Codex saw its first modern edition published in 1944 by Walter Muir Whitehill, in collaboration with the Spanish Consejo Superior de Investigaciones Científicas, including additional studies on its music and miniatures.
On July 3, 2011, the Codex was stolen from the Cathedral of Santiago de Compostela, and recovered on July 4, 2012, in a former cathedral employee’s garage. The former employee, who was thought to be behind the theft and other misdemeanors, was convicted in 2015 –and given ten years in prison.
But what’s in it?

The Santiago de Compostela copy of the Codex has five volumes and two appendices, for a grand total of 225 double-sided folios. It was restored in 1966, with the oversized pages trimmed and Book IV (which was removed in 1609) reinstated. The opening letter describes how the manuscript was gathered together, and how it survived various hazards.
Book I: Book of the Liturgies – This is the largest section of the Codex, and contains sermons and homilies on Saint James, descriptions of his martyrdom, and official liturgies for his veneration.
Book II: Book of the Miracles – This book includes 22 miracles attributed to Saint James, experienced by pilgrims across Europe.
Book III: Transfer of the Body to Santiago – This is the shortest book of the Codex. It tells the story of the transfer of Saint James’ body from Jerusalem to his tomb in Galicia.
Book IV: The History of Charlemagne and Roland – This is the Historia Caroli Magni, which tells the story of Charlemagne’s campaign in Spain and the legend of Saint James urging him to find his tomb.
Book V: A Guide for the Traveller – This book offers practical advice for pilgrims, describing the route, relics, sanctuaries, and potential scams. It is considered the first travel guidebook.