With its fast-moving narrative and resourceful, sympathetic hero, it is a book of almost universal appeal. But his apparently artless tale also embodies a vast and complex economic doctrine which Karl Marx, amongst many others, has thought worthy of serious scrutiny. It is, moreover, a work of considerable moral and religious significance; a fine tension is set up between God's purpose and Crusoe's building human impulses , which Defoe expresses with superbly vibrant, haunting realism.