You will find my books related to my Twitter Research in my Librarything Collection. They contain books on data science, social network analysis, statistical methods, programming and research methods.
by Robert Hanneman and Mark Riddle. 2005. Their website contains an excellent free introductory textbook on social network analysis: http://www.faculty.ucr.edu/~hanneman/ You can read it online or download the zip file version.
by By David Easley and Jon Kleinberg. Networks, Crowds, and Markets combines different scientific perspectives in its approach to understanding networks and behavior. Drawing on ideas from economics, sociology, computing and information science, and applied mathematics, it describes the emerging field of study that is growing at the interface of all these areas, addressing fundamental questions about how the social, economic, and technological worlds are connected. You can obtain a PDF version of the book from here.
Marc Smith from connected action has generated an amazon repository on social network analysis books.
The people at UCLA Acedemic Technology Services have created the greatest ever made collection of statistics books. You should definitely take a look at their extensive (> 10.000 titles) AND perfectly organized list of statistics books.
There is a very nice thread on quora where people recommend their favorite books about SNA http://www.quora.com/What-are-the-best-books-or-papers-on-social-network-theory-or-analysis