Just finished reading 'Zarrella's Hierarchy of Contagiousness: The Science, Design, and Engineering of Contagious Ideas'.
It's short (100 page) book that looks at the spread of ideas from a scientific (statistical) viewpoint. Of particular interest to me are the lists of keywords that result in retweets and Facebok sharing. It's good to read a new media marketing book that focuses on experiments and results, rather than fluffy ideas.
A bitesize read that's worth a couple of quid on Kindle: http://www.amazon.co.uk/Zarrellas-Hierarchy-Contagiousness-Engineering-ebook/dp/B005BP1Y36/ref=sr_1_1?ie=UTF8&qid=1319366882&sr=8-1
(or $3.15: http://www.amazon.com/Zarrellas-Hierarchy-Contagiousness-Engineering-ebook/dp/B005BP1Y36/ref=sr_1_2?ie=UTF8&qid=1319367118&sr=8-2)