Tony Horwitz (Ron Charles/The Washington Post)

Brown’s deadly attack with 18 fellow radicals on the federal armory in 1859 helped precipitate the Civil War. Abolitionists rallied to the cause; others, in the North and the South, were shocked by his violent tactics. When pressed to characterize Brown as an American hero or an American terrorist, Horwitz refused. “He was neither,” he said. “Or both. He was a complicated man.”

Unfortunately, none of the guests came dressed as Civil War soldiers, a la Horwitz’s “Confederates in the Attic,” but an alcoholic punch labeled “John Brown’s Body” was on tap.

To kick off his book tour, Horwitz will read from and sign copies of “Midnight Rising” at Politics & Prose on Monday night. The book officially publishes this week in the shadow — the author ruefully joked — of giant books about Apple founder Steve Jobs and former secretary of state Condoleezza Rice. But he needn’t worry too much: Civil War books are perennially popular, and he’s no stranger to the best-seller list himself.

Horwitz and his older brother, Josh, the president of Living Planet Books, look so much alike they could be each other’s stunt doubles. They still banter like the boys who grew up in Washington and attended the Sidwell Friends School. Their parents and The Post’s Joel Achenbach and Bob Woodward were among the guests Saturday night. Horwitz’s wife, the Pulitzer Prize-winning novelist Geraldine Brooks, remained at home with their two sons in Martha’s Vineyard. “Sometimes,” Horwitz sighed, “we have to do serial parenting.”