Rich Ling offers us Castell's latest research, and says this long PDF is "a pretty massive analysis of research on mobile communication. If you don't have any books for the beach, this might be the one." I know Castells to be thoughtful, insightful, and thorough. Castells, M., Fernandez-Ardevol, M., Qiu, J. L., & Sey, A. (2004) The mobile communication society: A cross-cultural analysis of available evidence on the social uses of wireless communication technology.
Via 'Mobile Society' digest