Efforts to systematize our knowledge of international relations (IR) have tended to focus on journal articles while ignoring books. In contrast, we argue that to know IR we must know IR books. To this end, this article presents the first systematic analysis of such books based on coding 500 IR texts published by leading presses against variables covering methodology, theoretical paradigm, and policy application. We compare the results with those of the Teaching, Research, and International Policy (TRIP) project's coding of 2,800 journal articles against the same variables, and the 2008 and 2011 TRIP surveys of more than 3,000 IR scholars. The main findings are that books are much less quantitative than articles published in leading journals, are somewhat more representative of the field according to paradigm, and are more engaged with policy concerns.