This transformation owed a great deal to a remarkable innovation in the book market, almost as significant for the development of libraries as printing itself: the book auction. … Booksellers assessed collections, compiled the catalogues and sold them in their shops, taking 5–15 per cent commission on sales. They even, less creditably, infiltrated some of their own slow-moving stock into the sale, where it could be passed off as part of the distinguished library going under the hammer.

Andrew Pettegree, Arthur der Weduwen, The Library- A Fragile Hist…, loc. 287