I think the best thing to do when you get to the really dense sections is just to plough through. It reaches a critical mass of crazy notation and mindbending logic in the middle, but once you get past that it drops back to being relatively graspable again as he addresses different areas. At least for a while :)

As I said, don't expect yourself to really understand all of it the first time you read it. Read it for the bits you do understand, not the bits you don't. Even if that turns out to only include the Carrol-esque dialogue, it's worth it.