Rastignac The Devil is a science fiction novel about the world in the 22nd century by Philip Jose Farmer.
Excerpt from the book:
"After the Apocalyptic War, the decimated remnants of the French huddled in the Loire Valley were gradually squeezed between two new and growing nations. The Colossus to the north was unfriendly and obviously intended to absorb the little New France. The Colossus to the south was friendly and offered to take the weak state into its confederation of republics as a full partner. A number of proud and independent French citizens feared that even the latter alternative meant the eventual transmutation of their tongue, religion and nationality into those of their southern neighbor. Seeking a way of salvation, they built six huge space-ships that would hold thirty thousand people, most of whom would be in deep freeze until they reached their destination."
