There were only four Wind at My Back chapter books published. These chapter books are very similar to the Road to Avonlea chapter books except there aren't any black and white photos in the middle of the book. The WaMB books are harder to find, but can be found in on-line bookstores. In the December 2007 video question and answer session with Kevin Sullivan, Kevin said that at some point they might look into republishing them.
Unlike the Road to Avonlea books, these chapter books are extremely similar to the episode. There are minor changes in words, but that's it. I was somewhat disappointed with Nerves of Steel. There is quite a bit a swearing in the book, and that seems odd to me since the book is intended for kids. My Dog Pal was the most different from it's episode in the fact that it gives who killed Pal.
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Wind at My Back was based on two books, Never Sleep Three in a Bed and The Night We Stole the Mounties Car, written by Max Braithwaite. You can find these books at on-line bookstores. I've never read the books, so I have no idea if they're any good.