An idea someone should do something with

You walk into a bookstore, a used bookstore. The books are not so much on display as piled. There is every kind of book, from philosophy to literature to cook books to children's stories. Sitting at the desk is a man smoking a pipe and reading something intently. You approach him to see what he's reading, and he raises his eyes above the cover to meet yours. Without prompting he closes the book to show you the front--something you've never seen or heard of before, by an author that sounds familiar, but you can't quite place. He points to the back of the store with the tip of his pipe, a long gray finger of smoke wearily extends his reach.

Not sure what all this means, you take the opportunity to leave him alone, and follow in the direction he has indicated. Eventually you reach a strange bookshelf at the back of the store. There are no books on it, but a sign above reads:

Place two books on the shelf. Choose carefully.
Looking around you notice a stack of books by Derrida and another by Borges. Seemingly at random you choose two, and place them on the shelf. Nothing happens. Behind you the man at the desk coughs loudly, and you turn, startled. He smiles at you through the smoke, and goes back to reading. You turn around to retrieve the books, only there are no longer two books, but one. You pick it up and notice that it is neither of the books you originally chose. It is neither of the two, and yet both of them at the same time. You open to a random page, and the prose is not Derrida or Borges, but both at once, melded into a single voice.

Realizing the potential of what you've found, you begin to comb the stacks of books all around, looking for two more books. Which books do you choose?