George John, 2nd Earl Spencer (1758-1834), was one of the greatest book collectors the world has ever known. He built upon the foundations of the family library at Althorp in Northamptonshire, which Dibdin estimated to contain some 7,000 volumes, including several rarities. However, he disposed of many of the books that his father, the first Earl Spencer, had collected in favour of better copies. Throughout his career George John was very willing to improve his collection in this way, and there were notable sales of duplicate and inferior copies from the Bibliotheca Spenceriana. He acquired several complete libraries by private treaty with their owners, and he purchased books through dealers and at auction, though he did not attend sales as frequently as some of his fellow collectors.
Spencer was fascinated by the classics and he eagerly sought first editions of all the principal Greek and Roman writers. One of his first significant purchases, in 1790, was the library of Count Reviczky, one-time ambassador of Maria Theresa in Warsaw. This was particularly rich in Aldine editions of the classics. The purchase cost Spencer a mere £2,500; he recouped some of the expense at a sale of duplicates in March 1790. Spencer bought heavily at the sensational Roxburghe sale of 18 May 1812, bidding against stiff competition from two of his chief rivals in book collecting, the Marquess of Blandford and the Duke of Devonshire. The celebrated Valdarfer Boccaccio eluded him, going to Blandford for the record sum of £2,260. However, when Blandford was forced to sell much of his collection seven years later at the White Knights Sale, Spencer was able to secure it for less than half that price. In 1813 Spencer paid £3,400 to Thomas Johnes of Hafod for the fine library previously assembled by Stanesby Alchorne, Controller of the Mint (d. 1800). This created further duplicates that were sold on 22 May 1813. In 1819-20 Spencer undertook a tour of Europe in quest of bibliographical rarities, in particular books produced by Sweynheym and Pannartz, the first printers in Italy. The high-point of the tour was Spencer's purchase of almost the entire library of the Neapolitan nobleman, the Duke di Cassano Serra. The duplicates from this collection were sold in 1821. It is estimated that by the time of Spencer's death the collection contained 10,000 Italian books of all periods, one quarter of the total.
From around 1805 Lord Spencer employed the services of Thomas Frognall Dibdin as his librarian and collecting agent. Dibdin's career as a bibliographer began in 1802 with the publication of his Introduction to the knowledge of rare and valuable editions of the Greek and Roman classics. This work attracted the notice of the Earl, who became his life-long patron and helped him secure ecclesiastical preferment. Dibdin's clerical career may have brought some advantage to Spencer himself, as his protégé had considerable success in eliciting books from religious houses. Dibdin published numerous works of bibliography, such as Bibliomania (1809, 1811), Bibliotheca Spenceriana (1814-1815), Bibliographical Decameron (1817), and Aedes Althorpianae (1822). Modern scholarship, however, has identified serious errors in Dibdin's cataloguing.
The Cassano Serra purchase signified the high-water mark of Spencer's book collecting. He continued to acquire books until his death in 1834, but the era of bibliomania was coming to an end. He could rest content that he had created the greatest library then in private hands, rich in incunabula, Bibles, Italian literature of the fifteen and sixteenth centuries, illustrated books, and examples of fine printing from all the major European presses. When George John Spencer died in 1834, his sons John Charles, 3rd Earl Spencer (1782-1845), and Frederick, 4th Earl Spencer (1798-1857), were content to leave the library intact. However, the agricultural depression of the 1880s compelled his grandson John Poyntz, 5th Earl Spencer (1835-1910), to sell the collection in 1892. He entrusted the sale to Edward Grose Hodge of Sotheby's. Amid considerable secrecy, Alexander Railton of Henry Sotheran & Co. negotiated on behalf of Mrs Enriqueta Augustina Rylands to purchase the collection almost in its entirety for the John Rylands Library. The revelation of the buyer's identity and of price she paid - £210,000 - caused a sensation, amid much relief that the collection had not been dispersed or sold abroad.
