The first Ellery Queen novel, The Roman Hat Mystery, was published in 1929. The cousins had entered a writing contest the year before and their entry had won but the magazine closed before the story was published. That didn't stop Dannay and Lee, though. They took their work to other publishers. The cousins based their character on a prominent detective of the era, Philo Vance, who was created by S.S. Van Dine (also a pseudonym).
Like Vance, Ellery Queen is something of a snob. He is Harvard-educated and remained aloof from the people in the cases he investigated. His deceased father was a street-tough New York Irishman but his mother was from a family of New York aristocrats. In later novels, though, Queen is depicted as somewhat more empathetic.
Queen was the hero and the "author" of more than 30 novels and several short story collections. A distinguishing feature of the novels was the Challenge to the Reader page that appeared near the end of the novel. It stated that the reader had seen all the same clues that Ellery Queen had seen and that there was only one correct conclusion. Could the reader solve the mystery?
Queen also was the "editor" of his own mystery magazine, and featured on radio, television, in the movies, in comic books and graphic novels, and in board games and jigsaw puzzles. The last Ellery Queen novel, A Fne and Private Place, was published in 1971.