This article examines the making of young Johannes Lomejer's treatise on library history De bibliothecis (1669) including the famous Chapter X in its second edition (1680) that is considered to be the f?irst comprehensive inventory on European libraries. Since this chapter has been thoroughly analysed by J.W. Montgomery already in 1962, the scope of this article is not its contents but the way it is related to Lomejer's personality and career, to his publications and the circulation of knowledge, and to his family habitus and the local network in which his work was embedded. The author shows that Lomejer, who most probably was educated by his uncle Christofffer, bookseller at Zutphen, could benef?it from a tradition of learning in his family and from a compact network of local scholars in the city in which he was successively teacher at the Latin school, Reformed minister and professor at the Illustrious School. Lomejer was a typical polyhistor, yet his work shows an interest in cultural practices that points to an early form of cultural history.© 2012 Koninklijke Brill NV, Leiden.