Microwave Engineering: Passive Circuits

This book is an excellent introductory text on microwave engineering for students and a great reference work for practicing engineers. It is very readable and while mathematically rigorous, is full of practical and useful material. It is limited in scope in that it doesn't address active devices or ferrites, but the treatment of transmission lines and passive microwave components is the most accessible and user-friendly I have found. Put it on your desk right next to Microwave Engineering by Pozar and Antennas by Kraus. It will probably be your first stop if you need a concise explanation or a quick refresher.