Life, the Universe and Everything is the third book in the six-volume Hitchhiker's Guide to the Galaxy science fiction "trilogy of five books" by British writer Douglas Adams. The title refers to the Answer to Life, the Universe, and Everything.

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.