Nordisk familjebok (Swedish: [ˈnuːɖɪsk faˈmɪljəˈbuːk], Nordic Family Book) is a Swedish encyclopedia that was published in print form between 1876 and 1957, and that is now fully available in digital form via Project Runeberg at Linköping University.
The first edition of Nordisk familjebok was published in 20 volumes between 1876 and 1899, and is known as the "Idun edition" because it bears a picture of Idun, the Norse mythologic goddess of spring and rejuvenation, on its cover. This was published during almost a quarter of a century, and particularity the first ten volumes contain material which are not seen in later editions. A good example of this is found in the end of the Berlin article. (which is included in the second volume, from 1878), the author finishes his article by telling about "countless of whiteness who find the public decency and morality to be very poor". The author continues by complaining about "the external ecclesiastical duties" as being "very lazy" and "to all these joint circumstances, one can hardly defend oneself against the thought of future threatening dangers".
The second edition, popularly known as Uggleupplagan ("The Owl Edition") because of an owl image on its cover, was published between 1904 and 1926 in 38 volumes, and is the most comprehensive encyclopedia published in the Swedish language.. 
The third edition had 17 volumes and was published between 1924 and 1937. Another three supplementary volumes were published in 1937, 1938 and in 1939. The supplement covers for instance the Spanish Civil War and a heavy update on Adolf Hitler, but nothing about Germany's war on Poland nor are later events are mentioned. A second printing of the entire third edition was published between 1941 and 1944. Nothing essential is changed in the second printing, but quite a lot of one side portraits (still in black and white), coloured maps of "World cities", European countries, continents, Swedish provinces and cities are added together with a few topics, like a collection of national flags. All the added material are on unnumbered pages, presumably a technical printing solution (so already printed books didn't require to be re-numbered). This edition is usually called "the 1930's edition" and are of brown colour when looking at them on a shelf.
Projekt Runeberg (Project Runeberg) was founded in by Lars Aronsson and others at Linköping University in late 1992. It was started with the intention of providing digital copies of books significant to the culture and history of Nordic countries (just as Project Gutenberg has done with English literature). By 2001, technology—image scanning and optical character recognition techniques—had improved enough to allow digitization of both print editions of the Nordisk familjebok (45,000 pages). While further work on this encyclopedia series remains (as of 1 January 2015), the two editions were freely available at the Project Runeberg web portal as of that date.