We had to hunt for the books.
There was no Amazon then, the major chains did yet include rare book services, and the University of Redlands bookstore certainly had no incentive to be useful. Instead we made book runs to Berkeley, where Cody's and Moe's were the beautiful Shining Cities on the Hill, and Cody's even had an upstairs room with originals in French.
There was a rumored text by Althusser, Essays in Self-Criticism, which was NLB but out of print and utterly impossible to find. I thought of it at the time as Hollywood later thought of Unobtainium: said to exist, but has anyone seen it? I searched Moe's many times over two or three years without success, until I found it, of all places, in a used bookstore outside the Greyhound station in Riverside. But that was the fun. There was a certain aleatory serendipity to one's resources pre-Internet. I loved the adventure of that.
There's a funny story which brought me closer to my mom my first summer home. From the pay phone in the hall I'd asked her to pick up copies for me of Lineages of the Absolutist State, For Marx, and Reading Capital, along with Burroughs and Bukowski and Bulgakov, the Three Bs. I correctly predicted the interesting HBJ storefront bookstore downtown would carry them all. Not knowing Althusser she naturally thought the title was "Four Marks", and was baffled until a helpful clerk set her straight. She thought that was hilarious and we had a good laugh over pizza one evening.
Nowadays you can get any OOP title from hundreds of used bookstores which sell through Amazon online. In this respect we live in a better world. But the old serendipity was fun, browsing bookshops outside bus stations was fun, and I miss the happy little buzz of randomly bumping into something really special.