The grassroots movement that started Sept. 17, 2011, with a protest in a park near Wall Street has mushroomed into a series of demonstrations in hundreds of cities around the world. In a year of protests from the Middle East to Madison, Wis., the Occupy uprising, a passionate outcry for economic justice, has been defined by its lack of definition. Now from TIME comes an illuminating collection of stories that answers many of the key questions about Occupy: How did it get started? What's behind the anger of the so-called 99% this group claims to represent? Who leads this leaderless movement? What should its agenda be? How can it transcend the occupation of tiny Zuccotti Park in lower Manhattan? "What Is Occupy? "includes chapters from the pages of TIME by columnists like Joe Klein and Rana Foroohar, as well as new chapters original to the book, plus the results of exclusive TIME polls.