This is a series of vignettes about a "what if the Roman Empire never fell" world, following the history of the postulated "eternal empire" from familiar ancient times through a more extrapolated "modern" empire. Not Silverberg's best effort, but interesting reading to fans of the alternate history genre.
Interesting actual speculative history, but the dialogue isn't very interesting.
This review is a little unfair, because I quit after reading the prologue. But on the other hand, it was so annoying that I couldn't bear to read past the prologue, and if someone out there has the same tastes I do, they'll probably not want to read past the prologue either.
I like alternate history. Lots, usually. And it's rare that I give up on a book at all, let alone an interesting-sounding alternate history after just a few pages. That tells you how much this annoyed me.
In the prologue, two Roman historians from the fifth century CE meet coincidentally while in the library and start discussing their research. So far, no problems. The POV character's friend's research is on the Hebrews of Egypt, and he spends the bulk of the prologue expounding on the idea that if that Hebrew leader Moshe's slave revolt and exodus had succeeded (instead of failing and leading to the Hebrews returning to slavery), then they might have made it back to their homeland. And then, he speculates, they might eventually have merged some of their religious ideas with other religious ideas of the region, particularly the idea of rebirth and resurrection influenced by their exposure to the worship of Osiris. And THEN this new religious movement might start up in Rome. And THEN it might start preaching universal love and communal property to everyone, and THEN it might sweep the Empire and bring the whole thing down.
Now how likely is it that anyone would correctly guess five out of five turning points that would lead to our own history, of which he has no knowledge? (Assuming, that is, that the enslavement of the Hebrews and the Exodus even happened on any large scale, which isn't independently confirmed.) How did he make the leap from "belief in rebirth" to "preaching universal love and communal property" out of all the possible other things his hypothetical fusion religion could preach? (I mean, why not more laws and rituals instead?)
It's just barely possible - but it's so unlikely that the whole prologue reveals itself to be nothing more than a device to tell us how this history is different from our own. It's clunky, and the fact that the author couldn't think of a way to work this exposition into the main narrative doesn't fill me with confidence in his writing skills. The historian character might as well just say, "As you know, Reader Bob, in your world it went like this, but in our world..." Or cut the characters altogether and just write a paragraph-long prologue explaining what happened! Who wants to read a book where the characters are turning to look at the audience and explaining what's going on all the time--and it ISN'T meant to be funny?