TWO NEW SCIENCE FICTION BOOKS reviewed in the Guardian have ancient classical themes. One, Roma Eterna, by Robert Silverberg, explores an alternate history in which the Exodus of the Hebrews from Egypt is delayed until the 28th century C.E., the Roman empire doesn't fall, and Christianity and Islam fail to become world religions. As I've mentioned before, the book I'm currently writing uses alternate history as a tool to analyze the transmission of the Old Testament Pseudepigrapha, so I'm interested in keeping track of such things. I think I read the chapter on Muhammad a few years ago when it was published as a short story. Robert Silverberg . . . well . . . Robert Silverberg rules.