I can truly recommend reading this book and learn more about Nikon CLS. The author describes very practically how to use flash and the CLS and helped me to improve my flash photography a lot. There is a section on every Nikon flash and transmitter unit which is partly interesting, because no one will have every device. The section on those devices I own were very good indeed and better written than the usual manual. Anyway, If you want to learn a few more things about using flash effectively you should read this book.