I definitely prefer the original two radio shows over any of the books.
Basically, in order of favorite to least favorite (edited after listening to all the radio shows again):
- 1978 Radio Show ("Primary Phase")
- The Hitchhiker's Guide to the Galaxy (1979 book)
- 2004 Radio Show ("Tertiary Phase")
- The Restaurant at the End of the Universe (1980 book)
- Life, the Universe and Everything (1982 book)
- 1979/1980 Radio Show ("Secondary Phase")
- 1981 TV Show
- 2005 Radio Show ("Quintessential Phase")
- 2005 Radio Show ("Quandary Phase")
- Mostly Harmless (1992 book)
- And Another Thing... (2008 non-Adams book)
- So Long, and Thanks for All the Fish (1984 book)
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- The Hitchhiker's Guide to the Galaxy (2005 film)