Over the south aisle of the nave is the cathedral library. It contains rare and valuable books and documents of great age, including King John's will and a book printed by Caxton who set up England's first printing press in 1477. It was not until 1461, in the time of Bishop Carpenter, that a library was erected, and then it was placed in the charnel house; but there were collections of books and manuscripts before that, some certainly kept in the cloisters.
When Archbishop Laud made his visitation in 1634 he complained that the chapel called 'Capella Carnaria' had been profaned and turned into a haybarn. Two years later it was fitted up as a school and the schoolhouse was converted into a library. The muniments and charters, far more numerous then than now, were obviously kept in the Edgar Tower and much neglected, for we are told that in 1635 Dean Mainwaring had saved thousands of rolls lying about in the tower, removing them from a damp stone wall and from under a window where rain beat in on them. In the same century, the library was moved to the light and spacious chapter house and began to be enriched by the addition of many interesting books. In 1771 Rev J Griffin, headmaster of the cathedral grammar school complied a catalogue which filled a large folio volume, but it was not until 1880 that a printed catalogue was produced. A later catalogue showed that the cathedral possessed 35 books printed beof4e 1500 and 277 volumes of medieval manuscripts. A second collection consisting of printed books numbers about 4,350, and there is a third collection of volumes of manuscripts, charters, accounts, court rolls, and other records.