Recently I noticed an uptick in one category of vintage books: Series books for girls from the 1930-60s. It seems many can't wait to load their bookshelves with original Nancy Drew hardcovers (in jackets, of course) and preferably, the older versions, the better (and costlier). Cost for original Nancy Drews seem to be no object these days. Think of that. (Nancy Drew book, last below, in original-though tattered- d/j is in the $100 range).
I've only managed to snag one or two early Nancy Drew mysteries in their original jackets, but I've had much better luck finding reasonably-priced, popular pictorial (laminated) girl detective series from the 1940s & '50s,. These books starred other female detectives like Donna Parker, Ginny Gordon, Trixie Belden, Polly French, the Dana Girls and Judy Bolton. One of my recent favorites, for more than one reason, is Ginny Gordon in The Lending Library Mystery. Even more attractive than the vintage prose of these girl-sleuthing books are the colorful covers . Most of them feature young women aggressively pursuing some one or something other than a chocolate soda at the Malt Shop.
I'm not 100% sure (maybe only 79%), but I think the popularity of these books of the past had something to do with changing girls' opinions about what they could to do when they grew up. As in, marriage was not the only option. In most of these series, finding a boyfriend was not nearly as important as finding a secret key or a hidden staircase. And there you have it: yet another likely reason for the feminist movement blossoming in the 1960s & '70s when young women like author Sue Grafton were sharpening their pencils.