A lot of what I read is out of print and sometimes I have to go to great lengths to acquire the books on my list. I have run afoul of UVA's Iliad system, trying to get books out of the Ivy Stacks warehouse. They did let me have Martin Boyd's Outbreak of Love, which could have been about some sort of health care crisis, but I was not allowed to have Isabella Bird's Six Months in the Sandwich Isles because it was not "work related." I try to remember which titles I'm having difficulty finding and will look through used book stores whenever I get a chance. My other sources for hard-to-find books are intralibrary loan and amazon.uk, which has books that are not available on amazon.com, usually with reasonable shipping rates.
Now, I have a new source, forgottenbooks, an online library that provides free access to nearly half a million titles. They contacted me with an offer of a lifetime membership and I have been having fun browsing there. You can search directly for a title or author, or browse among twenty-five categories, including fiction, drama, foreign language, and the very tempting "home and household books." (I love old books about cooking and domestic chores.) You can also search for images. Once you've found an interesting book, you can read it online, download a PDF, or download it to your kindle. There are also mobile apps available. Each book also comes with citation styles for MLA and APA, which is a great feature for students! Since you can search back to 1500, Forgotten Books is probably a great resource students who need primary source material for a paper.
Do you ever find yourself searching for books that went out of print long ago?