It's everywhere: from the laws of citizenship to the detection of doping in sport, from the books of the Old Testament and the acts of Macbeth to the mudbloods of Harry Potter and the vampires of Twilight. Blood fills our imagination, just as fully as it fills our veins. In this provocative exploration of the medical and social history of blood, from ancient times to today, award-winning novelist Lawrence Hill considers blood's scientific, cultural, psychological and political aspects. He charts how our understanding of blood has developed over the centuries, sharing a close-up view of William Harvey's bloody dissection table at which the seventeenth-century physician shocked his peers, using a live dog to prove that blood circulates. But blood isn't just about the body, and Hill also reveals how ideas about blood purity have spawned rules on who gets to belong to a family, who enjoys the rights of citizenship and what defines a person's identity. As Hill powerfully and lyrically conveys, blood counts in virtually every aspect of our being that matters.