Some previous posts have noted the online presence of scans of important Thomistic texts. I just recently came across the HathiTrust Digital Library, a free repository of online books. A quick search for Thomistic-related items using the “full-view” option revealed a few items, such as the first 28 volumes of Revue thomiste (split up here and here), several classic Marquette Aquinas Lectures (e.g., Owens, Phelan, Maritain, Bourke, Adler, Régis), the occasional Latin text, and most of the Summa contra Gentiles in English.
There are many great texts available in similar repositories like Internet Archive and Google Books. There is some overlap between the three sites, and sometimes one scan will be full view on one site but preview-only on another, so it is best to look around. (With some surprise, I discovered that all of Johannes Capreolus’s Defensiones is available in Google Books – this means the text is searchable!). With just a computer, it seems, one now has more access to books than a certain famous wealthy Renaissance bibliophile.
Might there be other substantive online repositories of scholarly books beyond HathiTrust, Internet Archive, and Google Books that should be mentioned here? Reader comments below are welcome.