The Center for Book Culture has what they claim to be the only interview of Gaddis published in the United States. Gaddis would only consent to be interviewed by mail, and it's a pretty short interview. Here's one of the better passages vis a vis Recognitions:
WG: The story that "The Recognitions" was edited down to its present size from a much longer manuscript must have gained currency from a hasty review of my papers by someone who came across fragments there that I'd rejected myself. In a work of that length and time in the writing some of it was rewritten repeatedly, some scarcely at all, some cut, tossed out, recovered and placed elsewhere, some later inserted, some sequences worried at and tossed out entire.