In the twentieth century, the number of private libraries rose sharply due to the increased levels in wealth and education, the increase in the number of works published and the improved organisation of the book trade. The book collectors' motivation remained the same as before: scholars brought together specialist libraries to support their academic work and amateurs collected in a certain area because of their love of books, with many variations in between the two.

As a result of the increased attention paid to the design of books, the meaning of the word 'bibliophile' changed. Until then, it had meant a lover of books in general, now it was used to describe someone who loved special, well-made books. Gradually it was also used to indicate the books themselves, i.e. editions in small print runs, with individual designs and printing and using special initials, fonts and illustrations, on special paper.

In the 1930s, the Netherlands had a number of collectors who specialised in collecting this kind of book. Often they not only collected modern bibliophile books, but manuscripts and rare and valuable older printed works as well. Sometimes they also financed bibliophile editions, as, for example, the scrap dealer M.B.B. Nijkerk, whose collection is now in the Stedelijk Museum in Amsterdam, and the passionate and well-to-do collector E. van der Borch van Verwolde. M.R. Radermacher Schorer's library contained so many bibliophile books that it formed the basis for the Museum van het Boek, established in 1960 and now part of the Museum Meermanno in The Hague. From the years following the Second World War we must mention the library of Johan B.W. Polak.

Radermacher Schorer united the two types of collector in one person: the bibliophile in the strict sense, but also the collector in the wider sense, i.e. someone who passionately gathers a collection in a certain area, in his case Dutch literature.

In the twentieth century, a large number of that second type of collector resided in the Netherlands who sometimes built up a collection in a recognised discipline, but more often they broke new ground with their collections. G.J. Boekenoogen and C.F. van Veen, for instance, each gathered a large collection of children's books. The fate of both collections is typical of what may happen to such collections after the death of the collector: Boekenoogen's collection was bought in its entirety by the Koninklijke Bibliotheek, resulting in a shift in focus in that library's collection policy; Van Veen's was auctioned at the collector's request. Another famous library is Joost Ritman's Bibliotheca Philosophica Hermetica, an exceptional library on hermetic philosophy, which was partly the reason for the establishment of a chair in hermetic philosophy at the University of Amsterdam. Thus book collectors and their collections can influence the policies of libraries and the direction of academic research.

Collectors often operate in anonymity. At the end of the twentieth century, the interest in them gradually increased. Newspapers and magazines such as De boekenwereld and De boekenpost published articles about them; a number of large libraries published books and catalogues about the collections they acquired and the collectors themselves united in 1994 in the Nederlands Genootschap van Bibliofielen.