Following his examen artium at Oslo Cathedral School in 1881 and his candidatus philologiæ in Kristiania in the fall of 1889,[3] Koren worked as a volunteer apprentice at the university library and a substitute at the National Archives.

[1][3] In 1896 he succeeded Niels Peter Selmer Arentz as librarian at the library of the Royal Norwegian Society of Sciences and Letters.

[1] It was Koren that acquired Thorvald Boeck's enormous book collection for the library in 1899.

At that time, Boeck's collection was the largest in Norway, consisting of approximately 31,000 volumes.

Koren persuaded the Storting to approve construction of a new building for the National Archives in 1929.