This slender volume attempts to present, as the preface says, a detailed review of the most important numerical analysis techniques for calculating modes and beam propagation in optical waveguides and fibers. If that's what you're after and you're not already expert in this area, it's well worth buying. The authors are both long-time practioners of these arcane arts in major Japanese firms, and it shows. On the other hand, it was originally written in Japanese and the authors are industrial researchers, not teachers; and to some extent that shows also. But I'm glad to have it, haven't encountered anything better in this area, and have no hesitation in recommending it.