- The Birth of the Republican Party in Illinois, 1854-1861 (2006)
- Lincoln and Lee at Antietam: The Civil War's Bloodiest Day (2010)
- The 14th Amendment and the Right to Vote (2014)
- Grant and Lee: A Study in Contrasts (2017)
- The Gettysburg Campaign and Culp's Hill: From Bloody Angle to Final Assault (2019)
In addition to his books, Collins has also written numerous articles and essays for scholarly journals and popular history magazines. He is a regular contributor to the Civil War Monitor, America's Civil War, and Hallowed Ground.
Collins is a graduate of the University of Maryland, College Park, where he earned a B.A. in history. He also holds a M.A. in history from the University of Virginia. He is currently a professor of history at Villanova University.