I urge you to take advantage of Jason’s generosity. I purchased a copy of his book when it first came out, and found it very helpful and informative. The free offer is for the second edition of the book, so you’ll get the “new, improved” version.
Get the free book by going to Jason’s Barefoot Running University site, and scrolling down to the bottom of the page. And then send a “thank you” to Jason – he deserves it.