For book publishers, retailers, and authors, the Digital Age has been an era of testing and uncertainty. The big question: Will new technologies be employed primarily to complement and streamline book publishing -- or will they undermine the business altogether? Two recent announcements illustrate the possibilities at the extremes: In one case, a publisher will simultaneously print a medical handbook and launch a Web site devoted to regular updates of the printed volume. In another instance, an author has announced that he will bypass publishers and retailers altogether, and send out his new novel in installments via e-mail. Readers of Simon & Schuster_s The Harvard Medical School Family Health Guide, to be published this fall, will be able to go to the book_s Web site and get new data that is keyed to sections of the manuscript. Free updates will contain breaking news about the causes of illness, diagnostic tests, pharmaceuticals and treatments, and directories of health organizations. Fans of the horror genre, meanwhile, will be treated to a techno-freebie. Starting in May, Douglas Clegg, author of "The Halloween Man" and other such works, will be sending out short, weekly installments of a new ghost story, Naomi, to all who request it. Clegg figures the approach could prompt him to produce his best work yet. "The fact that there are people out there waiting for it every week means a pressure that is creative and healthy," he says.