I can see you’ve already looked it up, but here’s a little more information. Yes, I refer to the book The Zahir, by Paulo Coelho:

A year later, I wake thinking about the story by Borges, about something which, once touched or seen, can never be forgotten, and which gradually so fills our thoughts that we are driven to madness. My Zahir is not a romantic metaphor — a blind man, a compass, a tiger, or a coin. It has a name, and her name is Esther.

Here, Coelho’s narrator refers to a short story of the same title, by Jorge Luis Borges. But the object of obsession in that story is a coin, which won’t do at all to describe a person, so I refer to Coelho’s Zahir.

The Zahir is one of Coelho’s less popular books, from what I can see; I received it as a gift and, to me, it is a thing of beauty.