My wife gave me a copy for Christmas to add to my collection (that includes both Structure and Touchstones).
My sense is that Odin Stone is even better than Touchstones. Or perhaps, I should say the reproduction in Odin Stone is better - the sense of place and sense of spirit that was so profound in Touchstones is still there in spades, but when you but the two books side by side, the reproduction of the images in Odin Stone is clearly superior.
All three books are awesome and inspiring. Tillman is a sensitive, thoughtful individual who has an uncanny ability to see strong images in ordinary places. His images are quiet and subtle and evocative of the spirit of the place where he found them.