The two biggest issues in the book are Buck's speech problems, and his interest in caving. Both are treated with care, and the research and background knowledge Naylor has of both of these is evident. I just wish that the excitement of the caving adventure had come much earlier in the book.
Some tighter editing would have made this a stronger story; there are a lot of things going on in the book that are less than interesting. The plywood stealing could have been cut out, and while the boys ridiculing Buck for his stutter were necessary to get him into the cave, it's hard to believe that this sort of behavior would have been tolerated by any adult in the picture. Buck's mother taking him to the faith healer also could have been cut. Naylor is such a good author that it seems rude to criticize her work. This was a good book that could have been even better.