In the early twentieth century, co-operation between publishers seldom took place. They did, however consult with one another and De Uitgever (The Publisher) (first volume 1918-1919) was a serious professional journal in which issues were discussed, but joint publications, as had been common in previous centuries, no longer occurred. The co-operation that eventually was to typify the twentieth century was of a different nature, i.e. increase in scale and the establishment of large publishing companies. In the sixties, the increase in scale was vertical, in other words, various branches of the industry merged. In the late seventies, eighties and nineties, we see a horizontal increase in scale in the formation of large publishing companies such as Wolters Kluwer, Reed-Elsevier, VNU, the PCM publishing group, Weekbladpersgroep and Bosch & Keuning. Already in 1980, a quarter of the 400 members of the KNUB had become part of one of these large companies, and that number continued to increase. Even writers' cooperative De Bezige Bij was taken over by the Weekbladpersgroep in 1997. In the eighties and nineties, the bookshops also worked together in purchasing syndicates such as Libris, Bruna and the Boekhandelsgroep Nederland (BGN).

A remarkable new form of co-operation in the twentieth century took place in the field of publicity and propaganda. The KVB and the Nederlandse Uitgeversbond were the most active in this respect. After all, the industry had a common opponent: the new recreational activities such as sports, cinema, radio, and later on discos, television and the Internet. There was also danger from the competing 'publishers' with their sales channels such as department stores, book clubs and broadcasting corporations. As early as 1910, 64 publishers took part in the National Exhibition of the Book in the Amsterdam Stedelijk Museum, a propaganda stunt. And they jointly published the annual catalogue Het Nederlandsche boek (The Dutch book) from 1924 to 1940. The mobile book exhibition on board the Orange train in 1933 and Dutch contributions to exhibitions abroad were also arranged by the Nederlandse Uitgeversbond. In October 1921 a literary supplement was issued by the NRC entitled Avondblad gewijd aan de letterkunde (Evening journal dedicated to literature). This was a publishers' initiative intended to inform readers, but after a few years the publication was discontinued. What survived longer was the committee for the (collective) Propaganda van het Nederlandse Boek (Propaganda of Dutch Books, CPNB), established in 1945 as a continuation of the Commissie voor de Collectieve Reclame (Committee for Collective Advertising, 1933). This committee included booksellers and publishers and, for instance, still organised the book week around the year 2000.

For individual publishers with their individual books, market research is unaffordable. To solve this problem, the umbrella organisation established the Speurwerk Foundation for Investigation Regarding Books in 1960, which carries out (market) research that is also beneficial to researchers (www.speurwerk.nl). Within the book trade itself, the study group 'Elspeet' was set up in 1959. Every year, 'Elspeet' brings employees of bookshops and publishers together to discuss issues.