The Monrepos library was originally collected in St. Petersburg by Strasbourg-born Ludwig Heinrich von Nicolai (1737–1820) and his son Paul von Nicolai (1776–1866). The library mainly contains literature from the 18th century and the beginning of 19th century. The sentimentality and early Romanticism of the late 18th century are also represented in the enlightenment-era library. It is a European "arts et lettres" library collected in Russia, which reflects both typical features of its time and its owner's personal interests.
Over half of the collection's books are in French, about fifth in German and there are also many works in English, Italian and Dutch.
The library was donated to the University of Helsinki during the First World War.