The conclusion drawn from the research run by Davis/Brewer, that electronic communication has both attributes of oral and written language is irrelevant, I guess, for most of today's electronic communication. The experiment performed by Davis/Brewer was in my opinion artificial (has anyone heard about mainframe software conferencing VAXNotes??) and has hardly anything to do with the way we use email / chatrooms / blogs, which were not yet there at that time (around 1990).
Therefore, I find this book's title overhyped and misleading, the content being far from issues of computer mediated communication and virtuality. On the positive side, authors have sound knowledge of today's linguistic theories. It is only hardcore linguists, who may somehow profit from this book. Anyone else should get an excellent Sherry Turkle's "Life on the Screen" instead.