This Doctoral Thesis analyses the use of Twitter as a new communication channel for the publishing sector, comparing the use of Twitter by US and Spanish book publishers. This research is an approach to the phenomenon of social networks in the publishing industry and the way in which publishers are using the channel to communicate with Twitter users. In addition to making a contribution to the evolution of Twitter from 2012-2015, it approaches the real potential of Twitter to disseminate messages and to obtain feedback from Twitter users. When considering these issues we are assessing the potential of using Twitter as a real time communication channel for companies, especially in the publishing industry, which allows interaction and direct relationship with potential readers. The interaction and direct communication with users is particularly interesting in the present context in which the publishers begin to settle in the digital universe and show a definitive bet of new forms of publishing formats including ebooks and multimedia applications. This research makes an important contribution to other research on social networks, because it gives clear quantitative conclusions that show the kind of communication that publishers are doing and what kind of message and content reaches a wider dissemination in the social network. Therefore, it can serve as a guide for publishers, and companies in general, who want to optimize the use of Twitter as a new direct communication channel with large audiences.