There is already a fair number of book about numpy (see Bibliography) and a legitimate question is to wonder if another book is really necessary. As you may have guessed by reading these lines, my personal answer is yes, mostly because I think there's room for a different approach concentrating on the migration from Python to numpy through vectorization. There is a lot of techniques that you don't find in books and such techniques are mostly learned through experience. The goal of this book is to explain some of them and to make you acquire experience in the process.