of these (equally "valid") approaches, and yet provides clarity about what kind of discourse or "reading" is in mind. 
He uses this language also in his earlier Old Testament Theology: Reading the Hebrew Bible as Christian Scripture (Baker Academic, 2013). Here is an extended passage (pp. 283-4) in which he explains its use. (I have taken the liberty of dividing up a fairly long paragraph--easier to read in print than "wall-of-text" on screen!):

It might help to pose the issue differently. In my discussions I have made use
  of the conceptuality of the world within, the world behind, and the world in
  front of the text. Almost all interpreters are interested, in one way or another,
  in the world within the text. The question becomes howone contextualizes
  this world within the text, which relates also to the nature of the imaginative
  moves that are brought to bear upon it.
The dominant move in modern
  biblical scholarship has been to relate the world within the text to the world
  behind the text—to look backward, as it were, from the Old Testament to the
  world that gave rise to it, the immediate world of Israel and also the wider
  world of the ancient Near East. This means, for the most part, a focus on
  times and places before ever there was an Old Testament, when at most there
  were incipient collections and compilations of material that only over time
  became Israel’s scriptures.
My approach, by contrast, has been