Before writing for Slate, Kaplan was a correspondent at the Boston Globe, reporting from Washington, D.C.; Moscow; and New York City.

He published Daydream Believers in 2008,[2] a work which analyzes the George W. Bush administration's use of Cold War tactics in post-9/11 military activities.

In late 2012, Kaplan published The Insurgents: David Petraeus and the Plot to Change the American Way of War,[3] which examines how General David Petraeus attempted to implement new thinking in Afghanistan and Iraq regarding the traditional clear and hold counter-insurgency strategy, and the shortcomings of this strategy, its intellectual underpinnings, and the individuals who defined it.

[6] The book argues that the course of world history was not changed by the counter-culture movements of the 1960s but rather by artistic, scientific, political, and economics events occurring in the year 1959.

Kaplan is an enthusiast of high-end audio and video equipment, and has reported from the Consumer Electronics Show on new technologies in this area,[7] as well as penning shopping-advice columns on which new televisions offer the best value.