The medieval university at Cambridge was a centre for the circulation of books. In complicated networks of acquisition and exchange, books were bought, borrowed, copied, and bequeathed. Colleges came to own collections of books for the use of their fellows, and in the late middle ages many colleges built library-rooms to house their books. Some colleges, notably Peterhouse, Gonville and Caius, and Pembroke, still retain large parts of their medieval collections. This volume collects for the first time all the medieval documents that refer to library holdings in both the medieval university and its colleges, documents as various as borrowing registers, inventories, and formal catalogues of various dates and degrees of sophistication. Also included is a substantial biographical section on individuals who gave or bequeathed books to Cambridge libraries, and where a will survives it is included as a document.