It was back in the 90s, a uni class I was teaching, and a boy and a girl were passing a book back and forth, pretty interested in it.
So as the manager of the activity that was going on, I set things up so I could go over to see what it was. They handed it to me freely. Not only various takes on '****', but many other things--such as "eat you out", "cowgirl style", and so on. With illustrations.
After realizing what it was, and probably blushing, I just handed it back and went back to what the rest of the class was doing. In retrospect, kudos that they were (or seemed to be) openly discussing that kind of thing.