In the concept of this book we faced a dilemma: should the structure of the book be from the general to the specific or vice versa? The obvious advantage of going from the general to the specific are that metodologies can be first developed in abstract and then applied to specific problems. Such a format, while being of benefit to seasoned researchers who wish to relate their own experience to a broader setting, is less user friendly for those who want to learn new techniques by working through engineering problems from the beginning to the end. Our choice has been to privilege the latter aspect, hence devising a pattern that, by starting from very simple problems, finally leads to the solution of very complex ones.

The book could well be divided into two main parts: the first four Chapters are of introductory type and are, in our opinion, useful to the relatively unfamiliar reader; they can be skipped from the more experienced researcher already aquainted with the topic. Chapters 5 to 8 are, instead, quite suitable also for the specialist since several techniques are introduced in these Chapters. In particular, Chapter 7 constitutes the main original contribution of the book since it contains the methodology on how to compute the complete spectrum of open non-separable waveguides. A few applications are illustrated in Chapter 8.

Although the titles of the various chapters should convey relatively clearly the subject addressed in each case, it is useful to provide a somewhat more detailed...