This, and it's sequel "By Schism Rent Asunder" are the best Sci Fi books that I've read recently.
Off Armageddon Reef starts with humanity on the losing end of a galactic war. Facing defeat and genocide, Earth comes up with a desparate scheme to hide a single colony. In order to escape detection, the colony is designed to be preindustrial, and its designers intend to keep it that way by instilling a religion and culture designed to prevent technological advances.
Centuries later, an AI wakens, and finds the colony stagnating. It then sets out on a multi-generational quest to bring humanity back to the stars and eventual victory, overturning a planetary church to do so...
These novels move between space travel, and battles among sailing fleets. The plots are complex, the characters are compelling, and the dialog is first rate. I don't have a single complaint.