The Life and Times of the Late Demon Rum purports to be the only "wet" history of the temperance movement; it covers Temperance from its earliest beginnings late in the eighteenth century up to the passage of the Eighteenth Amendment and national prohibition.
Two of his books, The Road to Harper's Ferry and Goodbye to Uncle Tom, deal with African American issues---The Road to Harper's Ferry is an account of John Brown's raid on Harper's Ferry, which delves into the lives and motivations of the "Secret Six" who gave him a great deal of his support, and Goodbye to Uncle Tom examines how Uncle Tom's Cabin, both as a novel and in its many stage adaptations, has shaped American attitudes towards African Americans and slavery.
He is credited with uncovering the truth behind the Lillian Hellman short story, "Julia," later made into a movie starring Jane Fonda and Vanessa Redgrave.
Hellman claimed the story was a true if veiled account drawn from the life of her childhood friend "Julia," a doctor trained in Vienna as a psychotherapist and an anti-Nazi.
Furnas died on June 3, 2001, at his home in the Stanton section of Readington Township, New Jersey.