This really is a classic.
Yeah, im another one who heard about the book through the KLF, but i also knew what the book was more or less about after hearing so much about it. I think i first read it 12 years ago, and again very recently.
The book is hilarious, Hagbard is the king of one liners, with an ace up his sleeve, i wont give the game away. The plot jumps around like crazy, often mid sentence, forwards and backwards in time, space, heads. It is a complex book and you do begin to wonder who all these people are, like Aleister Crowley, and John Dillinger, all real people, and real events, all tied in with believably wonderful conspiracy theories.
I do remember the first time i read it, i was a bit annoyed with the ending, but seeing as i knew the ending the last time i read it, i enjoyed it much more and the ending actually made sense to me, why not end it like that? Utter genius!
My last reading of it was done entirely in the bath, from beginning to end, which took a fair while i will admit, but the book is just so witty and clever that it is hard to put down, even if its been read before.
This is in my top 12 books of all time, just to let you know =o)