The Illuminatus! Trilogy, by authors Robert Anton Wilson and Robert Shea, is a very, very strange book with tons of weird characters, crazy events, fictional and bizarre twists on historical happenings, and all kinds of nonsense that barely makes sense at times. At other times everything seems to fall into perfect place and reveal the secret to the entire story, and then everything is smashed to pieces again.
The book is full of conspiracy theory and really ties the characters and events together quite nicely. I usually recommend this book to anyone that hasn't heard of or read any of RAW's books before because it is definitely one of his most polished and complex novels and it is amazing that two author's collaborated to write it. The only real weakness that the book has is that it can be a bit boring at times and the story is a bit long, but overall it is a marvelous piece of work.
This was the first book that I read by Robert Anton Wilson and it has impacted me in quite a few ways. The humor alone is worth the investment.