In <em>The Gun Gap</em>, Mark R. Joslyn advances gun owners as a new classification for understanding political behavior and attitudes. He demonstrates a "gun gap," which captures the differences between gun owners and non-gun owners, and shows how this gap improves conventional behavioral and attitudinal models. The gap represents an important explanation for voter choice, voter turnout, perceptions of personal and public safety, preferences for gun control policies, and support for the death penalty. Moreover, the 2016 presidential election witnessed the largest recorded gun gap in history. <em>The Gun Gap</em> thus affords a new and compelling vantage point to evaluate modern mass politics.