Like the other reviewers, I loved this book. It will keep you interested in running for a long time to come. Henderson makes sense.But I want to make sure that serious runners know what the book is really about. It's not a book about developing a competitive edge--at least not in the normal sense. It's not about living on the edge--in terms of high mileage training. It's about not falling off the edge--that is, staying healthy and interested in running over the long haul.As much as I loved the book, I couldn't give it 5 stars because right now I'm in the competitive mode, determined to qualify and run the Boston Marathon. I need more tough training right now than Henderson promotes.Once I run Boston, I'll come back to this book and love it more than ever.