I’m about halfway through The Illuminatus! Trilogy, and the most apt description is, if you’ll pardon the language, a mindfuck. Once the writing settles into a coherent structure (or perhaps once the reader is attuned to it), the mind starts noticing connections. Everywhere. It’s as if it was written specifically to induce apophenia.
The most insidious part of the book(s) is the frequent use of historical or other authors’ fictional sources. “Oh, there’s Emperor Norton.” “OK, we’re back to Buckminster Fuller again.” “Hey, that’s right, ‘Tekeli-li!’ does show up in both Lovecraft and Poe.” And this constant mixing of fact with fiction, familiar with strange, and things known to be true with things which seem implausible does make you wonder: how much of this did they make up on their own, and how much did they stitch together out of real events, prior works, and creative synthesis?