Sam Atkinson, House Leaves also has some form of "Tertiary" World

In House of Leaves, there is a form of Tertiary world in that there is a great deal of fake academic writings within the novel which explain the strange phenomena within the book. Without spoiling anything for those of you have not read it, much of it is written in the form of scientific research regarding strange shadows and noises which appear due to physical properties of our universe. This sort of third academic framework doesn't just serve as simply explanatory though. It also serves as a further story as what happens to those researching such things gives new light to the occurrences in the novel. This tertiary world thing is an interesting device, which upon further reflection, is actually fairly common.