Miracle at Belleau Wood: The Birth of the Modern U.S. Marine Corps (Lyons Press, 2007) (A Main Selection of the Military Book Club)
Horrid Pit: The Battle of the Crater, the Civil War's Cruelest Mission (Carroll & Graf, 2007)
Blooding at Great Meadows: Young George Washington and the Battle that Shaped the Man (Running Press, 2006)
Profiles in Audacity: Great Decisions and How They Were Made (Sterling, 2006)
Patton: A Biography (Palgrave Macmillan's Great Generals Series, 2006), series editor General Wesley K. Clark
Thomas Jefferson (Alpha “Critical Lives” series biography, 2001)
Benito Mussolini (Alpha “Critical Lives” series biography, 2001)
Astronomy (Oryx Frontiers of Science Series) (with Christopher De Pree) (Oryx, 2000)
Complete Idiot's Guide to Criminology (Macmillan/Alpha, 2002)
Complete Idiot's Guide to World War I (Macmillan/Alpha, 2000)
Complete Idiot's Guide to the 20th Century (Macmillan/Alpha, 1999)
Complete Idiot's Guide to the American Revolution (Macmillan/Alpha, 1999)
Complete Idiot's Guide to Jazz (Macmillan/Alpha, 1999)
Complete Idiot's Guide to Astronomy (with Christopher De Pree) (Macmillan/Alpha, 1999; Second Edition, 2001)
Complete Idiot's Guide to the Civil War (Macmillan/Alpha, 1998)
Complete Idiot's Guide to Mixing Drinks (Macmillan/Alpha, 1998)
Complete Idiot's Guide to American History (Macmillan/Alpha, 1996; Second Edition, 2000)
My Brother's Face: Portraits of the Civil War (with Charles Phillips; Chronicle Books, 1993)
What Everyone Should Know About the 20th Century: 200 Events That Shaped Our Time (with Charles Phillips; Adams, 1993)
Songs of the Wild West (Simon and Schuster/Metropolitan Museum of Art, 1992)
The War between the Spies: A History of Espionage During the American Civil War (Atlantic Monthly Press, 1992)
A Chronicle of the Indian Wars: From Colonial Times to Wounded Knee (Prentice-Hall Press, 1992)
What Every American Should Know About American History: 200 Events That Shaped the Nation (with Charles Phillips; Adams, 1992)
Art of the Golden West (Abbeville Press, 1991)