There are approximately 4,750 books printed before 1820 in the Parker Library, of which around 1,075 are from the collection of Archbishop Matthew Parker (1504-1575).

The collection covers a wide range of subjects, but is unsurprisingly particularly strong in sixteenth-century church history and the writings of the Reformers. It is now catalogued to modern bibliographical standards, with extensive indexing enabling searching by subject, provenance and binder where applicable.

Between April 2003 and April 2006 these books were recatalogued online by William Hale, Parker-Taylor Bibliographer, in a project generously funded by Dr. John Taylor, an old member of the College. A secondary objective of the cataloguing project was to determine as far as possible which of the books in the collection are from the library of Archbishop Parker and which are from other sources. A list of Parker's printed books was compiled as part of the project, and is now available in the Library; details of other former owners is available for download on the side menu. 

Bibliographical records for the Parker Library’s early printed book collection have been incorporated into the University of Cambridge’s online union catalogue, iDiscover, and are also available via COPAC.  Most of the Parker Library books are found in the standard bibliographical reference works (such as Adams, STC, Wing, ESTC and ISTC) but a list has been compiled of those that are not included in these works, which is available for download on the side menu.