'The advantage of this book is to give both [the semi-classical and the full quantum] approaches, starting with the first, illustrated by several simple examples, and introducing progressively the second, clearly showing why it is essential for understanding certain phenomena ... I believe that this challenge to present and to illustrate both approaches in a single book has been taken up successfully ... I have the highest admiration for [the authors'] enthusiasm, their scientific rigor, their ability to give simple and precise physical explanations, and their quest to illuminate clearly the difficult points of the subject without oversimplification.' Claude Cohen-Tannoudji, from the Foreword