Book excerpt: Not simply an investigation into melancholy, these unique essays form part of a panoramic celebration of human behaviour from the time of the ancients to the Renaissance. God, devils, old age, diet, drunkenness, love and beauty are each given equal consideration in this all-encompassing examination of the human condition. Throughout history, some books have changed the world. They have transformed the way we see ourselves – and each other. They have inspired debate, dissent, war and revolution. They have enlightened, outraged, provoked and comforted. They have enriched lives – and destroyed them. Now Penguin brings you the works of the great thinkers, pioneers, radicals and visionaries whose ideas shook civilization and helped make us who we are.