Title: Worlds of the Imperium
Author: Keith Laumer
Publish Date: 1962 Original Publishing
Publisher: Ace Doubleday
Sub-Genre: Alternate Universe Travel, Technology, Battles, Alternative Societies, Abduction, Entropy (Time Travel), Aliens
Along the 0-0 Universe timeline, the civilization of that Earth has discovered how to travel sideways across alternative timelines where the further you go from 0-0, or ‘Base’, the more extreme the differences in the way life developed.
Within the closer timelines are places, things, and even people that are very similar to each other. Brion Bayard was one of those people that existed in those timelines, and he is abducted from his own timeline by those of the Base in order to replace the world leader in an aggressive timeline that had the ability to detonate bombs in the Base one.
His mission was to travel to the rebel timeline and replace the dictator, removing the threat to the 0-0 timeline. But unknown to them all, the dictator wasn’t the real threat. The true problem was the 0-0 leadership itself.
Brion was a diplomat in Stockholm minding his duties when he was kidnapped, or rather shanghaied, and taken to a different world. Same planet, but a different timeline of the same planet, with many similarities, and many differences.
Different parallel timelines exist, and each one is different based on when different events in their history cause a divergence from a common history point.
People from one of those timelines successfully discovered a way travel between those timelines. Another timeline has nuclear bombs, and the ability to travel across timelines as well.
Brion has been brought to timeline 0-0, Stockholm to help them stop he renegade timeline from using its bombs from destroying their world. Brion’s counterpart in the other timeline is the dictator of that world and if Brion could assassinate him, and take over, he could save 0-0. Or at least that was the original plan. The problem is 0-0 didn’t know that the dictator had lost his legs before Brion was smuggled into his castle to replace him.
Discovered by rebel factions in the renegade timeline, Brion is spirited out of the castle and dropped into the middle of a rebellion. One of the rebel leaders thinks the renegade world can be his own playground. Somehow Brion has to smooth out the rebellion, and stabilize the world, then stop the bombs from being transported to 0-0.
Different universes coexisting at the same time have been an attractive premise for Science Fiction stories for a very long time.