Orbis

Orbis, Scott Mackay, Roc Books, 2002

Several thousand years ago, bodiless beings called the Benefactors came to Earth. Having the ability to take over human bodies, they attached themselves to one of the religious sects operating in the area of the eastern Mediterranean Sea, a sect which became Christianity. Two thousand years ago, the Benefactors fought a major war against the Romans, the rulers at the time, forcing the Romans to flee to the stars.

In the mid-20th century, the Benefactors rule under a benevolent dictatorship (but still a dictatorship) on the North American continent. This book takes place in the Missouri-Arkansas Territory of the Papal States of America. Most of the continent is off limits to P.S.A. citizens. The mere possession of parts to build a radio, or a Latin-English dictionary, are hanging offenses. Two senior members of the "church" travel into the Restricted Zone, contact the Romans by radio, and ask for help. The Romans have started to spread radio beacons throughout the galaxy because they have lost the knowledge of their origin. The Romans return to Earth, and defeat the Benefactors.

If life under the Benefactors is bad, life under the Romans is much worse. All young people are sent north to work in the iron mines, to pay for the Roman occupation. Any mother who refuses to send her child gets both hands chopped off. Those who remain are virtual slaves. A new insurgency is started among those who are left, Plains indian tribes (who live in the Restricted Zone), a more "liberal" Roman general, and the last of the Benefactors, who has been very influenced by the person whose body was taken over. Can they succeed, especially when told that 50,000 Roman troops will be arriving within days?

This one has some good alternate history ideas, and it's an interesting speculation about Christianity. It gets rather bloody by the end, but it certainly belongs in that large gray area of Pretty Good or Worth Reading.