The Guggenheim Museum has made many ebooks available for free through the Internet Archive.
"MetPublications is a portal to The Met's comprehensive publishing program with over 1,500 titles, including books, online publications, and Bulletins and Journals from the last five decades... MetPublications includes a description and table of contents for most titles, as well as information about the authors, reviews, awards, and links to related Met titles by author and by theme. Current book titles that are in-print may be previewed and fully searched online, with a link to purchase the book. The full contents of almost all other book titles may be read online, searched, or downloaded as a PDF. Many of these out-of-print books will be available for purchase, when rights permit, through print-on-demand capabilities in association with Yale University Press. For the Met's Bulletin, all but the most recent issue can be downloaded as a PDF. For the Met's Journal, all individual articles and entire volumes can be downloaded as a PDF."
Search tip: If you are researching a Met object, try finding the accession number in the Met's Collection database, and use the accession number to do a keyword search in MetPublications.
Torrossa: Casalini full text platform
Online resource offering full text access to Italian and Spanish books, conference proceedings, and journals by major Italian and Spanish publishers. Torrossa includes material previously available through Editoria Italiana online.