in the increasingly inaccurately named Hitchhiker's Trilogy". In addition, the blurb on the fifth book describes it as "the book that gives a whole new meaning to the word 'trilogy. The plots of the television and radio series are more or less the same as that of the first two novels, though some of the events occur in a different order and many of the details are changed. Much of parts five and six of the radio series were written by John Lloyd, but his material did not make it into the other versions of the story and is not included here. Many consider the books' version of events to be definitive because they are the most readily accessible and widely distributed version of the story. However, they are not the final version that Adams produced. Before his death from a heart attack on 11 May 2001, Adams was considering writing a sixth novel in the Hitchhiker's series. He was working on a third Dirk Gently novel, under the working title The Salmon of Doubt, but felt that the book was not working and abandoned it. In an interview, he said some of the ideas in the book might fit better in the Hitchhiker's series, and suggested he might rework those ideas into a sixth book in that series. He described Mostly Harmless as "a very bleak book" and said he "would love to finish Hitchhiker on a slightly more upbeat note". Adams also remarked that if he were to write a sixth instalment, he would at least start with all the characters in the same place. Eoin Colfer, who wrote the sixth book in the Hitchhiker's series in 2008–09, used this latter concept but none of the plot ideas from The Salmon of Doubt. The Hitchhiker's Guide to the Galaxy The first book was adapted from the first four radio episodes (the Primary Phase), with Arthur being rescued from Earth's destruction by Ford, meeting Zaphod and Trillian, coming to the planet of Magrathea and discovering the true purpose of Earth, and ending with the group preparing to go to the Restaurant at the End of the Universe. 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. The book reached number one on the book charts in only its