With Anne Marshall's appointment as his replacement in 2022, Marszalek was named Executive Director Emeritus of the Ulysses S. Grant Association.

[1][5] His research has primarily focused on the American Civil War, specifically Civil War generals Ulysses S. Grant, William T. Sherman, and Henry Halleck, but he has also written on local Mississippi history, the history of racial conflict at West Point, and the Eaton affair.

Marszalek's book Sherman: A Soldier's Passion for Order was a finalist for the 1993 Lincoln Prize.

[7] On April 13, 2018, Marszalek won the Nevins-Freeman Award, the most prestigious honor given by The Civil War Round Table of Chicago.

[8][9] Showtime made Marszalek's book Court Martial: A Black Man in America, into the motion picture Assault at West Point: The Court-Martial of Johnson Whittaker.