A key part of the Truman presidency will get a closer look Thursday night.

A.J. Baime’s new book is “The Accidental President: Harry Truman and the Four Months that Changed the World.” He speaks at 6:30 p.m. Thursday at the Unity Temple, 707 W. 47th St. on the Plaza. It’s free, but go to trumanlibraryinstitute.org to register.

The focus of Baime’s book is the first four months Truman was president, a period that included the end of World War II in Europe, the Potsdam Conference that greatly shaped Europe after the war, the signing of the United Nations Charter, the dropping of the atomic bomb and the end of the war against Japan.

Baime’s previous books include “The Arsenal of Democracy: FDR, Detroit, and an Epic Quest to Arm an America at War” and “Go Like Hell: Ford, Ferrari, and Their Battle for Speed and Glory at Le Mans.”