Linked + Six Degrees - two books on networks
Titles: Linked: How Everything Is Connected to Everything Else and What It Means for Business, Science, and Everyday Life and Six Degrees: The New Science of Networks
Authors: Albert-Lászlo Barabási (Linked) and Duncan Watts (Six Degrees)
Genre: Popular Science/sociology/networks
Readability: Linked is very easy to digest, Six Degrees is at times more academic.
Two recent books I have read about the emerging science of networks, as it is applied to areas such as social networks and the diffusion of ideas, the spread of AIDS and other epidemics, and the structure of the internet.
Linked is the best of the two books. It is eminently readable, serving its findings in neatly chopped up chapters with lots of interesting case stories. Examples range from the story of Patient Zero of the AIDS epidemic (a homosexual flight attendant called Gaetan Dugas who bonked his way though innumerable airport lounges) to the Kevin Bacon game and the classic experiments of Stanley Milgram, who first discovered the 'Six Degrees of Separation' effect. It is a very good introduction to the subject.
Watt's Six Degrees is also well written and covers basically the same subjects, but goes more into the technical details of the science. One thing it does offer, though, is a fascinating insight into how you can use math to gain important insights from a theory. I've gotten more interested in math as a consequence of reading this; previously, I didn't really understand the value of mathemathical modelling in testing scientific theories. (He also wrote a scientific version of the same book, called 'Small Worlds', which is full of equations and obviously intended only for math students or similar. I didn't read it.)
Buying both books doesn't make sense, so if you are interested, go with Linked unless you are curious about mathematical modelling.