FD just finished reading a recent (2008) novel by the prolific Robert Barnard called Last Post. The title refers not to the end of postal service, but to a last letter sent to a woman already dead. The letter is the starting point for the entire plot. Though FD will not be recommending the novel as a must-read, Mr. Barnard is to be applauded for continuing to use actual letters in constructing a novel set in the present day.
It’s a bit ironic — many of the very early novels in English were composed of letters, since the authors knew that readers, who themselves were writers and readers of letters, could be helped to suspend their disbelief if offered the “letters” of the characters in the novel. Several kind bloggers have made lists of epistolary novels, including this one and this one.
A few of today’s novelists have tried to incorporate email into novels in a similar way as letters have been used (see for example John Crowley’s Lord Byron’s Novel [links to reviews available here]) but FD has not found this persuasive. And there are probably novels being written if not already published in which text messages play a similar role. And may be equally unsatisfying!