The Hitchhiker's Guide to the Galaxy is the first book in the Hitchhiker's Guide to the Galaxy comedy science fiction "trilogy of five books" by Douglas Adams, with a sixth book written by Eoin Colfer. The novel is an adaptation of the first four parts of Adams's radio series of the same name, centering on the adventures of the only man to survive the destruction of Earth; while roaming outer space, he comes to learn the truth behind Earth's existence. The novel was first published in London on 12 October 1979. It sold 250,000 copies in the first three months.The namesake of the novel is The Hitchhiker's Guide to the Galaxy, a fictional guide book for hitchhikers (inspired by the Hitch-hiker's Guide to Europe) written in the form of an encyclopaedia.