Some pretty convincing photos inside. Plus info about how people feel when near them, like nauseous or peaceful. I'm glad they included a couple that were man-made to compare against as some people think they're all man-made.
This book reckons that they're made by electric currents coming from the earth in swirls but i think its ufo's.
If anyone's interested you could probably google it, but there are apparently ice-circles found where the water won't freeze again and the pattern stays a long time. Its not in this book but i thought i'd mention it anyway.