Recently on eBay, an advertising sign sold for a nice sum featuring vintage Nancy Drew book art and just a few titles. A fellow collector was the winner of this neat collectible and are we not just all jealous:) haha! I'd love to see more of this advertising come on the market, hopefully more will follow.
Recently, I have been collecting vintage Nancy Drew book ads at eBay. There are quite a few sellers that purchase whole catalogs from eBay and other sources and break them down into separate pages to sell individually. As a book collector that can make me cringe, but it is to my gain that I'm able to purchase just the ad I want and not have to spend the larger amount on buying the whole catalog. I've been amassing quite a few ads from old Sears, JC Penny, Wards and the like. Even an old Milton Bradley catalog featuring the 1950s Nancy Drew boardgame.
In the interest of research, I also came across a website which has been scanning old catalogs and uploading the pages. I was able to print pretty decent copies of pages of old ads from this source to ad to my collection. Here's the link:
A lot of other series were advertised besides Nancy Drew including Three Investigators, Hardy Boys, Dana Girls, and Cherry Ames! The earliest example I have is from 1935 Sears and features the Nancy Drew book, The Message in the Hollow Oak.
Search eBay for neat ads like these!