Over at Overweening Generalist, Michael Johnson has written an interesting roundup of ideas about the writer William Burroughs. (Burroughs' birthday was Feb. 5). Johnson documents some of the ways that Burroughs influenced Robert Anton Wilson.
Burroughs' work popularized the cut-up prose technique invented by Brion Gysin. Although I don't see a mention of Illuminatus! in this article about cut-up technique from Wikipedia, Illuminatus! would probably count as a prominent example of the technique. Wilson also used it on other occasions.