I also recommend these few books as a good starting point:
Network Science: Theory and Applications[2]
Linked: How Everything Is Connected to Everything Else and What It Means[3]
Six Degrees: The Science of a Connected Age[4]
The Wisdom of Crowds[5]
Nexus: Small Worlds and the Groundbreaking Science of Networks[6]
Diffusion of Innovations[7]
Of course - being that Network Science is a multidisciplinary field, that touches a lot of other areas - it can be hard to get a handle on what to study. But those few books - between them - cover a lot of the basics and would give somebody who's interested in this stuff enough background to figure out where to start digging deeper.
For a little bit more on the technical side, a couple of good resources at:
Introductory Graph Theory[8]
Introduction to Graph Theory[9]
Algorithms in Java: Part 5 - Graph Algorithms[10]
[1]: http://en.wikipedia.org/wiki/Network_theory
[2]: http://www.amazon.com/Network-Science-Applications-Ted-Lewis...
[3]: http://www.amazon.com/Linked-Everything-Connected-Else-Means...
[4]: http://www.amazon.com/Six-Degrees-Science-Connected-Edition/...
[5]: http://www.amazon.com/The-Wisdom-Crowds-James-Surowiecki/dp/...
[6]: http://www.amazon.com/Nexus-Worlds-Groundbreaking-Science-Ne...
[7]: http://www.amazon.com/Diffusion-Innovations-5th-Everett-Roge...
[8]: http://www.amazon.com/Introductory-Graph-Theory-Gary-Chartra...
[9]: http://www.amazon.com/Introduction-Graph-Theory-Dover-Mathem...
[10]: http://www.amazon.com/Algorithms-Java-Part-Graph-Pt-5/dp/020...
Networks, Crowds, and Markets: Reasoning About a Highly Connected World.
In case epistemology and history are your kind of thing, I most highly recommend reading [2], one of the best book I read on the subject.
[1] http://en.wikipedia.org/wiki/Network_science
[2] L. C. Freeman, The development of social network analysis. Booksurge Llc, 2004.