Koula by Menis Koumandareas, a Greek novelist, tells the story of an affair between a young university student and an older woman who works for Greek IRS. They meet on the subway, where they often ride in the same car. Eventually, the begin to talk. Soon enough, they are carrying on an affair. The woman, Koula, becomes obsessed with the younger man. Realizing it, she breaks off the affair despite, or because of, her genuine affection for the younger man.
I read this during the Readathon for the Orbis Terrarum Challenge. It's pretty good novella, but not spectacular. But at 88 pages, it's a good read for the Readathon.