The Guggenheim has digitized 65 art catalogs and made them available online, free of charge. These texts include introductions to artists such as Kandinsky, Calder, and Munch as well as thematic introductions to modern art. Many of them contain full-color images.
If you have trouble using the online reader format (which includes an interactive page-turning feature), you can download PDFs and other versions at Archive.org.
Via Open Culture.