It took me doing a reading group to get through that one. That was more my fault than the book, but GEB is real work, and having a number of people involved definitely helped me stick through the parts where I might have wandered off for brain candy.
I think it took me four tries before I finally read it all the way through. Eventually the text on formal systems becomes quite heavy and that's where I stopped in my previous tries... once I got past that hump it was downhill all the way. Highly worth the effort; one of the best books I've ever read.