"Too often our only knowledge about American history is remembered from childhood," says This American Life radio commentator Sarah Vowell, whose most recent book, Assassination Vacation ($21, Simon & Schuster), recounts her travels from Florida to Alaska to visit all manner of monuments related to the headline-making murders of Presidents Lincoln, Garfield, and McKinley. The book constructs a portrait of America in the 40 years after the Civil War but reads like a renegade field trip for grown-ups. Vowell treks to obvious places, such as Washington, D.C., the site of the Lincoln and Garfield shootings, and Buffalo, New York's Pan-American Expo grounds, where McKinley was assassinated in 1901. She also visits more obscure sites, such as a museum in a Maryland house once occupied by a John Wilkes Booth collaborator and the Adirondack mountain that Vice President Teddy Roosevelt was climbing when he heard of McKinley's shooting. Vowell's favorite stop?The Oneida mansion, in upstate New York. This former residence of Garfield's assassin was also the headquarters for a 19th-century utopian free-love community. Bet you didn't learn that in elementary school.