The Library, that since 1995 is administered by the Fondazione Ranieri di Sorbello, is based on the XVIII Century collections of several person belonging to the ancient house of Bourbon Del Monte di Sorbello, in particular Uguccione III (1737-1816), Diomede (1743-1811) and Ugolino (1745-1809).
The first inventory, of about 3000 volumes, dates back to 1802.
It bestows - at the date of June 2015 – about 23.000 books, with monographies and miscellanies, among which an exquisite ancient fund of about 500 editions of manuscript and printed works of the centuries V-XVII and a gathering of various documents in the archives.
Recently the Library has been enlarged thanks to deposits of scholars and family collections and it is still now been enriched with new acquisitions.
Since 1998, when it was opened to the public, it acquired the connotation of a specialized Library, intended for qualified and specific studies.
The Historic Family Archives (X-XX Centuries), was given to the State Archives of Perugia, where it is still held in deposit, while other family papers (XVII-XX Centuries) as the Uguccione Ranieri di Sorbello Fund (1906-1969), the photographic Archives and the Alleati Archives, are still held at the Fondazione Ranieri di Sorbello, together with other Funds of later acquisition.