The Plains of Abraham — Stephen Parrish

The first volume of the Abraham trilogy. René Jordan and Father Malcolm Marchand are caught hoarding forbidden books in post-apocalyptic Kebek. They escape to Ellanoy and what appears to be a Utopia. During their stay Ellanoy is attacked by an army of warriors descended from less fortunate survivors of the poisoned rains. Utopia isn't so utopian after all.