Founded in 1911, the AAVSO boasts over 1200 members and observers and is the world's largest non-profit organization dedicated to variable star observation. This timely book marks the AAVSO's centennial year, presenting an authoritative and accurate history of this important association. Writing in an engaging and accessible style, the authors move chronologically through five eras of the AAVSO, discussing the evolution of its structure and purpose. Throughout the text, the main focus is on the thousands of individuals whose contributions have made the AAVSO's progress possible. Describing a century of interaction between amateur and professional astronomers, the authors celebrate the collaborative relationships that have existed over the years. As the definitive history of the first hundred years of the AAVSO, this text has broad appeal and will be of interest to amateur and professional astronomers, as well as historians and sociologists of science in general.