During the past months I was from time to time reading all kind of stuff related to networking and security. During this process I came accross this book:
I found this book to be very comprehensive and very modern in sense of current topics across the "network universe". If you ever wanted to get a more deep insight in how routers communicate with each other or how to setup a VoIP infrastructure, this book is a must. Not only it provides very useful information to specific topics but it also shows how to configure stuff using Cisco and Juniper hardware. At the end of each topic you'll get a short summary and a list of questions aimed at helping you to understand and internalize the material.
All in one a really good (e-)book on advanced networking, accompanied by good explanations and visualizations.