The Metropolitan Museum of Art hosts 372 art history books online. All of the books can be read online or downloaded as PDFs (warning, some of them are massive files). You can search through the catalog of books by thematic category, format, and publication type. And, of course, you can search through the books by title, author, and keyword.

This page includes links to each of the individual Music Theory pages I've created in PDF form. This is a work in progress; I am writing new ones regularly and fixing errors and omissions on existing ones as I find them. If you find them useful for your theory studies, you are welcome to use them, and if you find errors or have suggestions, I invite you to contact me. Enjoy! These pages are available for free under a Creative Commons BY-NC-ND license.