One of the most influential physicists of our time, Stephen Hawking touched the lives of millions. Recalling his nearly two decades as Hawking's collaborator and friend, Leonard Mlodinow brings this complex man into focus in a unique and deeply personal portrayal. We meet Hawking the genius, who uncovers the mysteries of the universe with a pathbreaking theory of black holes; Hawking the colleague, whose illness leaves him able to communicate at only six words per minute but who expends the effort to punctuate his conversations with humor; and Hawking the friend, who can convey volumes with a frown, a smile, or simply a raised eyebrow. Modinow puts us in the room as Hawking indulges his passion for wine and curry, shares his feelings on love, death, and disability, and grapples with deep questions of philosophy and physics. This deeply affecting account of a friendship teaches us not just about the nature and practice of physics but also about life and the human capacity to overcome daunting obstacles.