Excellent book with deep insight into coupling area of microwave world. From microwave network theory, characteristics of planar transmission lines to exact explanations of uniformly coupled lines, broadband forward-wave directional couplers, parallel-coupled TEM directional couplers , nonuniform broadband TEM directional couplers ... You can also find theory for developement of coupled-line filters, baluns , problematics of multiconductor transmission lines and high-speed interconnections. This is bible for coupling structures in many ways. It is very applicable as base for calculating and developement of any kind of real couplers. Very interesting and helpfull. It is a little bit more theoretical with a lack of enough practical calculations, but always explainable to deepest basement of problematics. Book for bookshelf in microwave lab.