At the end of the sixteenth century the Dutch Republic was a country where only scholars and the odd nobleman possessed a few hundred books. Hundred years later, several hundred private collections came under the hammer every year. Many book-historical, economic and social reasons have been put forward to explain the rapid development of book auctions in the Netherlands but a single prerequisite is often overlooked: growth such as this could only be possible after an equally rapid growth of private ownership of books.

The oldest surviving (but probably not the very first) printed auction catalogue of a private library dates from 1599 (Philips Marnix van Sint Aldegonde). Growth was rapid after that: for the period between 1601 and 1610, 26 auction catalogues of private libraries have been preserved (including anonymous ones), and for the years 1701-1710 that number rises to 153 and these are only the extant catalogues. It has been calculated that the chance of survival for an auction catalogue from this period is less than 20%.

Auction catalogues are the most important source of knowledge about private libraries which no longer exist. There are a handful of printed catalogues extant which were not intended to promote the sale of the collection described and, hidden in archives, a great many hand-written inventories which were drawn up during the settlement of legacies or bankruptcies can be found, but as far as accessibility, accuracy and reliability is concerned, printed auction catalogues win easily. In the database of Bert van Selms project Nederlandse boekhandelscatalogi tot 1800 (Book Sales Catalogues of the Dutch Republic, 1599-1800), almost 1800 catalogues are recorded for the period under review of which about 1300 are presented as at least partially consisting of the collections of one or more named persons; the other 500 are anonymous collections of unclear provenance. Some 1460 of these have been published on microfiche in 2008. These catalogues must of course be used with the greatest caution in the reconstruction of book ownership for a specific person (they are often incomplete, or - on the contrary - complicated by additional material) but they are extremely useful in determining what kind of person possessed what kind of book, because not only can it be determined which work was involved but usually also which edition. Estate inventories, however, are different. For example, the 160 entries in the inventory list drawn up in 1677 by a notary of the books in the Spinoza estate were classified according to format but often consist of author's name only and seldom give a place or year of publication, making guesswork of determining in which edition the philosopher read his Pliny or Seneca.

Ownership of books was widespread in the Netherlands. Among the owners of - often large - private collections were not only scholars and professors, academics (clergymen, lawyers and notaries, doctors) but also surprisingly many well-to-do citizens such as merchants, magistrates and civil servants. Books needed professionally by some were not available in the small and not very numerous university libraries or town libraries, so they had to be purchased, or borrowed from private individuals. In fact, the private library as we know it from the auction catalogues was often much larger and richer than was either useful or necessary for professional purposes or for entertainment. It must be true bibliophily that emanates from the printed catalogue the merchant, diplomat and magistrate, Adriaan Pauw, had printed in 1654 of his rich library (16,000 titles) but, in many other cases, the well-provided, 'complete' library - just as a portrait by Rembrandt or a stately home on the river Vecht - would have been a status symbol for a citizen of Holland and, perhaps, also a good investment.