"In this new book about Online Social Networks, the authors discuss the way that the social brain places limits on how we express and use relationships on Twitter and Facebook. Through the analysis of the users' personal ego networks, the book shows how cognitive constraints are visible in the emergent properties of the graph of OSNs.

As with the real world, so with cyberspace. We can only deal with just so-many "friends", and we can only follow just-so many threads. Of course, the narrow characterization of links as friends hides the actual strength of the graph-edge: it can be something that is oft-used, or a rarely trod track; a node at either end may be core to a cluster or peripheral; things change over time. I want to say "cogito ego sum", but better I refer the reader to the analysis of the structural properties of OSNs in this very useful and timely book." --Jon Crowcroft, Computer Lab, University of Cambridge, UK

"Since its birth in the mid 90’s, Dunbar’s hypothesis on the limits of human brain to support active social relations –150 at most – has fostered wide interest and debate. Now, teaming with computer scientists Arnaboldi, Conti and Passarella from the Italian National Research Council, the British anthropologist provides further quantitative evidence to his theory. Based on big network data from Facebook and Twitter, the authors explore the structure and mechanics of ego networks – the web of social contacts surrounding each individual person – discovering that the patterns predicted by Dunbar’s theory are in fact existing in the social networks that we humans re-created online. An influential result, which reveals the microscopic structure of society. Deep, stimulating, vivid. This book is an intellectual delight." --Dino Pedreschi, KDD Lab, Dept. of Computer Science, University of Pisa, Italy