From the description in the article, the book that the teacher gave to the student(s) is
The Sisters of APF by Zane. A quick look at the Amazon review indicates that the book has nothing to do with algebra.
I remember text-only porno books like that from when I was a teenager. They were typically sold to traveling-salesman types in places like airports and bus stations. They were really dirty, too.
I hadn't heard that women were not only fans of such 'literary' experiences, but had even become authors. You learn something new every day...
-ccm