I did it this afternoon while my baby was sleeping: I finished the book. I kept wanting to turn the pages, and pretty soon the spot where I was reading was a very long ways away from where I had been studying the many many interesting things that this book has to offer. I now plan to go back to the beginning with my notebook and my Book of Centuries in hand and probably look at a lot more maps... there's a LOT in this book, and I don't know enough about geography or Chinese history or even European history to follow everything that's in there. I'm also planning to make some visits to his 1421 website to see what I can see there. This stuff is fascinating!
It does raise the question: what do I teach my children about the discoveries of the various places in the world when it comes time to do that? If this book is right, and with all the evidence he has including diaries from the European explorers it sure is convincing, then all of the history textbooks need to re-written in a spectacular fashion.