Not only the mathematical content gets hard,
but the book is full of puns, metalinguistics, crossreferences, good enough to make you laugh out loud and subtle enough to not become saturated.
Yeah, what's striking is that the book itself is an example of what the book covers. For example, read the last page, then go to the first page.
Has he talked much about his writing process for this book? Would be really interested to read his thoughts on it.
He talks in length about his writing process in the preface to my edition. I think it's the 20th.