In “The Road” a boy and his father lurch across the cold, wretched, wet, corpse-strewn, ashen landscape of a post-apocalyptic world. The imagery is brutal even by Cormac McCarthy’s high standards for despair. This parable is also trenchant and terrifying, written with stripped-down urgency and fueled by the force of a universal nightmare. “The Road” would be pure misery if not for its stunning, savage beauty.