Sorry for bringing back this old thread, but here's some information for someone who doesn't want to spend $60 on the book.
If you're in school, or have a kid in school, try and get the book ordered through the school. They will send 1 free copy to any school that requests it, and you don't have to pay anything but the $10 shipping fees. Great way to save $60 on a must-have book.
"Fifteen hundred years ago everybody knew the Earth was the center of the universe. Five hundred years ago, everybody knew the earth was flat, and fifteen minutes ago, you knew that humans were alone on this planet. Imagine what you'll know tomorrow"