Living in NYC I am surrounded by so much art, that there is no way to encompass it. Yet in the years after WWII I grew up in Southern California, then pretty much a cultural desert. How does someone in the provinces learn about art? There were of course the art magazines, but since they were not usually sold on newsstands, in high school I was oblivious to their existence. But, haunting the public libraries as it did, books I knew about.
There were four significant publishers in those days. First, was a grand institution, Phaidon Press, started in the 1920s in Vienna and successfully transplanted to England. I remember being struck by their edition of Berenson's Italian Painters of the Renaissance. Even though I subsequently lost my enthusiasm for BB, that was a start. There were also books by the Museum of Modern Art, with the Picasso one hitting the bull's-eye for me. Most of these books had few or any color plates. But the somewhat garish Skira books from Switzerland were all illustrated in color. Color too was the favorite of the New York publisher Harry N. Abrams, who published two major works by Meyer Schapiro, on Van Gogh and Cézanne.
Today, art publishing seems more diffuse, with most books printed in Asia, so there is less dependence on a few sources.
A friend notes the role of museum sites on line nowadays. They are good and getting better, but how many know about them? There is also for better or worse the role of the book as a commodity.