The combination of broad humanistic references, speculative spirit, elegant (sometimes poetic) style and (last and, for me, least)careful mathematical explanation makes this a really extraordinary book. I was totally engrossed in it while reading, and have found myself rethinking many of the ideas since I finished it. I look forward to re-reading it in perhaps six months. I'm sure I'll discover yet more richness that I missed the first time around. This book is not for everyone, but if you have the intellectual energy to invest, you'll be amply rewarded. All in all, it's a wonderful celebration of what the human mind is capable of at its most expansive.