In the nature of its collections the John Rylands Library is akin to independent research libraries in America such as the Huntington and Folger. Its nucleus is the Althorp Library, founded by the 2nd Earl Spencer and one of the most famous private libraries of all time. Its holdings in history, literature, theology and historical bibliography are particularly remarkable both for the incunabula period and the centuries beyond.

The microfiche edition reproduces the 4,000 page catalogue of the Library's holdings at its founding in 1899, together with nearly 500,000 slips recording acquisitions up to 1978.