Another claim seems to be that a collection of unread books serves as a personal reminder of ignorance, that the un-known always exceeds the known, a kind of "memento ignorantiae" that gives us the humility and motivation to always seek to learn more rather than remain complacently content with the knowledge we have already acquired.
And possibly the physicality of a dead-tree library carries this effect more forcibly than an online shopping list.
Then when I want to read one, I buy it. Then I read it.
I admit sometimes I hate a book so much I don't finish it and buy another, but I don't think that's the kind of unread book being talked about.
Maybe it's not nonsense, actually, is this article just some kind of post hoc justification for impulse buying tons of books?