Leinwand has created a practical guide to how school leaders can and should support reform in mathematics education. He uses the "baby and the bath water" as a metaphor for the things that modern math curriculum need to keep and to throw out. The most specific example that he uses several times through out the book is related to computation. He argues effectively that calculators and computers have made multi-digit paper and pencil computations "bath water," but single digit multiplication by three or four digits and division by a single digit are "baby" because they can be used to build conceptual understanding and estimation skills necessary for using and making sense of the operations with a calculator. He then goes on to give concrete but fairly general advise about the ideas, structures, and policies that should be in place to support change in classroom experiences for children. Overall, I agree whole-heartedly with his concept of "Sensible Mathematics" and the ideas for supporting the change are good. But in general they are too thin to build a robust change effort on alone. They are more a framework, that requires a good bit of creation to make practical, but I suppose that is necessary to make a book like this accessible to so many different readers.
I really like what this book has to say. Now to use/internalize 10% of it and I will be happy. Math instruction isn't what it used to be as the times change so does how we teach mathematics change.