Who is the most important and disruptive leader in the world today? Most Americans would probably answer, Donald Trump -- with Russia’s Vladimir Putin running a close second. But my choice for the must-read book of 2018, Elizabeth C. Economy’s “The Third Revolution,” makes a strong case that China’s Xi Jinping may deserve the title.Under Xi’s leadership since 2012, an increasingly powerful China has begun throwing its weight around in ways that have led international observers to fear the emergence of a new Cold War -- or perhaps even a new hot war -- with the US Xi has more candidly announced China’s ambitions to take center stage in world affairs than any leader since Mao Zedong; he has also amassed greater personal power than any Chinese leader since Mao. Economy’s book traces Xi’s influence and ambitions through an exhaustive reading of his speeches as well as an astute knowledge of Chinese politics and policy. It should be required reading not just for China-watchers but for anyone interested in US-China relations and the future of world order.Economy, a senior fellow at the Council on Foreign Relations, catalogs the changes China has experienced under Xi: The replacement of collective leadership with personalized rule, the constriction of the political system, the efforts to tightly restrict the flow of ideas into China while expanding the stream of ideas and influence rushing out of it. Economy is also a reliable guide to Xi’s seemingly contradictory efforts to stimulate game-changing, high-tech innovation while also steadily increasing the role of the Communist Party in China’s economy and society.Turning from the domestic to the foreign, Economy provides a concise discussion of China’s expanding military footprint, push to create new international institutions such as the Asian Infrastructure Investment Bank, launching of the Belt and Road Initiative and other major geo-economic projects, increasing use of coercive diplomacy toward its neighbors, and other efforts to project influence not just in the Asia-Pacific but globally. All of these undertakings seem impressive at first glance, and Xi’s vision seems to be carrying the day in Chinese politics for now. But as Economy reminds us, all the elements of his agenda -- from his grab for unchallenged individual authority to his drive for greater power and prestige overseas -- carry the danger of provoking a backlash, whether from dissatisfied rivals at home or wary competitors abroad, that could ultimately waylay Xi’s ‘Chinese Dream.’ALSO READ: Xi Jinping declares 'overwhelming victory' over graft in China: State mediaPerhaps the most valuable part of the book takes us from the realm of hard power to the realm of ideas. As Economy points out, Xi is advancing an ambitious ideological vision: ‘A uniquely Chinese model” that will “perhaps become a standard bearer for other countries disenchanted with the American and European models of liberal democracy.’ That model may seem to cut against the flow of the post-World War II era, in which the world has become progressively more democratic. Yet it actually fits quite well with the more recent propensity of things, as democracy has receded, the allure of the American liberal-capitalist model has faded, China’s economic performance has wowed developing countries around the world, and authoritarian ideas make a resurgence. Economy’s book is thus a useful reminder that of all the ways China is testing American leadership, this ideological challenge may ultimately be the most important, and the hardest, for the US to handle.