Lucy Pringle lets these photos speak for themselves - she simply notes the place, the pattern, and the "medium" - ie whether the artwork was produced on wheat or barley. Virtually no attempt to explain or analyse or compare - just allow them to sink in and let the images work their own magic. She picks 90 of the best aerial photos of works from 1993 to 2006 - with some close-ups as well. Some of the formations were so amazing that I gasped - I had never seen some of these in the press. A beautiful book and a great gift.
If you want more information after this, buy Freddy Silva's book "Secrets in the Fields" - a very calm and methodical academic research into the phenomenon with lots of detail that will help you understand what is going on. And it ain't two guys with a plank and a chain, be very assured of that.