In The Hitchhiker’s Guide to the Galaxy (published in 1979), the characters visit the legendary planet Magrathea, home to the now-collapsed planet-building industry, and meet Slartibartfast, a planetary coastline designer who was responsible for the fjords of Norway. Through archival recordings, he relates the story of a race of hyper-intelligent pan-dimensional beings who built a computer named Deep Thought to calculate the Answer to the Ultimate Question of Life, the Universe, and Everything. When the answer was revealed to be 42, Deep Thought explained that the answer was incomprehensible because the beings didn’t know what they were asking. It went on to predict that another computer, more powerful than itself would be made and designed by it to calculate the question for the answer. (Later on, referencing this, Adams would create the 42 Puzzle, a puzzle which could be approached in multiple ways, all yielding the answer 42.)
The computer, often mistaken for a planet (because of its size and use of biological components), was the Earth, and was destroyed by Vogons to make way for a hyperspatial express route five minutes before the conclusion of its 10-million-year program. Two members of the race of hyper-intelligent pan-dimensional beings who commissioned the Earth in the first place disguise themselves as Trillian’s mice, and want to dissect Arthur’s brain to help reconstruct the question, since he was part of the Earth’s matrix moments before it was destroyed, and so he is likely to have part of the question buried in his brain. Trillian is also human but had left Earth six months previously with Zaphod Beeblebrox, President of the Galaxy. The protagonists escape, setting course for “The Restaurant at the End of the Universe”. The mice, in Arthur’s absence, create a phony question since it is too troublesome for them to wait 10 million years again just to cash in on a lucrative deal.

The book was adapted from the first four radio episodes. It was first published in 1979, initially in paperback, by Pan Books, after BBC Publishing had turned down the offer of publishing a novelisation, an action they would later regret.[17] The book reached number one on the book charts in only its second week, and sold over 250,000 copies within three months of its release. A hardback edition was published by Harmony Books, a division of Random House in the United States in October 1980, and the 1981 US paperback edition was promoted by the give-away of 3,000 free copies in the magazine Rolling Stone to build word of mouth. In 2005, Del Rey Books rereleased the Hitchhiker series with new covers for the release of the 2005 movie. To date, it has sold over 14 million copies.