The Hitchhikers Guide to The Galaxy (novel)

The trilogy-in-six-books by Douglas Adams and Eoin Colfer. Probably the best-known and most "complete" version of the story.

The first book, The Hitchhikers Guide to The Galaxy, was adapted straight from the radio shows. It covers Arthur Dent's last day on Earth, meeting with the other characters, questing for the legendary planet of Magrathea, and the story of Deep Thought.

The second, The Hitchhikers Guide to The Galaxy, also came from the radio version, although with many more changes and a shifting-about of the order of events. These first two books can, in many ways, be thought of as halves of the same story, in a way that the sequels aren't. In Restaurant, the characters visit Milliways, the titular establishment at the rear end of time, Zaphod and Trillian attempt to discover who truly runs the universe, and Ford and Arthur end up on a spaceship full of useless people which crashes into prehistoric Earth.

The third book, Life The Universe And Everything, is the most conventionally adventure-ish book of the series; not surprising, since it was adapted from an unused Doctor Who script. Ford and Arthur get pulled back to modern-day Earth, pre-explosion, where Slartbartifast enlists them and, eventually, the rest of the cast to stop the machinations of the xenophobic Krikkitmen, who, at the dawn of galactic civilzation, were responsible for the bloodiest war the universe has ever seen, but who were sealed in a slow-time bubble... until now.

The fourth book, So Long And Thanks For All The Fish, is, on the other hand, probably the most character-based of the series. Arthur returns to an unexpectedly-resurrected Earth, but after his adventures among the stars, he's just as out of his element here as he was when he first hitched a ride on a spaceship.

The fifth, Mostly Harmless, is a dark romp through the corridors of probability. The Guide has been taken over by the Vogons, and Arthur has lost his love and has settled in as a sandwich-maker in a primitive tribe on a faraway planet. But then Trillian shows up with a surprise -- a teenage daughter, conceived with Arthur's donated DNA.

A sixth book, And Another Thing was written by Eoin Colfer, author of the Artemis Fowl children's novels, and published in October 2009. Starting where Mostly Harmless left off, the tone of the book in general is much lighter and removes the downer ending the series ended with. Whether this is an improvement is, of course, a matter of opinion.

For all versions of the story, see The Hitchhikers Guide to The Galaxy.

The books contain examples of:
 * Author Existence Failure (The books were technically completed, but Adams reportedly regreted the dark ending of the last book and wanted to write another, but his death prevented that.)
 * Creator Breakdown (Mostly Harmless)
 * Downer Ending (Mostly Harmless)
 * Single Line of Descent (Subverted with a minor character who's "the only living descendant of Genghis Khan", who dies along with the rest of the Earth and has no further bearing on the plot.)
 * Trilogy Creep