What's a good book or website for studying networking essentials?

I’m taking ITN101 and have a test in a few days. The test is written, not multiple choice and is based on “Guide to Networking Essentials” by Gregory Tomsho. The book is HUGE and isn’t exactly clear on a lot of things. It rambles a lot and isn’t really easy to study. I kind of need something to study the basics (devices, security, the OSI model, types of networks, topology, protocol, binary etc) and memorize what I need good enough to write a few sentences on it. Thoughts, anyone?