In 1848, Jón Árnason was appointed librarian at the Reykjavik Stiptisbókasafn, later to be called the National Library, and held that position alongside other occupations until he retired in 1887. He was the first employee of the library, but previously he had been a member of the library's board of directors.

The library was formally established in 1818 and opened for use in 1825. It was housed in the Cathedral attic until 1881 when it was moved to the Althingi House. In the cathedral attic, the library shared housing with the National Museum, which was established in 1863, but Árnason also took care of it together with painter Sigurður Guðmundsson.

The library's facilities were rather cramped in the cathedral attic, and Árnason complained for years about it and others in letters to the library's board committee. Despite difficult circumstances, Árnason managed to organize the library well and in 1881 he estimated that the collection included about 13.000 volumes.

Árnason performed all kinds of work at the library, as he was the only employee of it until 1882, but nevertheless he enjoyed the assistance of student Páll Pálsson during a period. The library was open twice a week, at noon on Saturdays and Wednesdays, and Árnason took care of the loans but also the ordering, cleaning and other things. However, the opening hours were extended after the library's relocation to the Althingi House in 1881. Árnason also received books, including from abroad, but many institutions and individuals sent publications to the museum, especially on the occasion of the 1000th anniversary of Iceland's settlement in 1874. Árnason published two printed registers (1874), one in manuscript (1849) and numerous additional bibliographies in the library's archives.

The Register of printed Icelandic books and manuscripts in the Reykjavik Stiptisbókasafn received a grant on the occasion of the national festival in 1874. In the register printed books were divided into ten categories, but manuscripts were organized according to size, and the manuscript register took over half the work and reached over 539 volumes. The register is accompanied by various documents related to Jón Árnason at an exhibition in the National and University Library until August 9.

The book can be viewed here.