Book Recommendations

Stanislaw Lem sometimes wrote very serious (Solaris) and sometimes very humorous. In particular, he wrote a series of comedic stories about a pair of inventors who were always trying to outdo each other with ridiculous inventions. In one story, another inventor builds an probability amplifier, to create dragons. (Which, apparently, are real but so rare that one would never naturally occur in the history of the universe.) Strange things result.

The probability generator story ("The Dragons of Probability") was in the collection "The Cyberiad", translated to English in 1974, four years before the earliest version of HHGtTG (the radio play). Adams claimed he was not aware of the Lem story when he wrote Hitchhiker's Guide.

Anyways, Lem is fantastic. I think "The Futurological Congress" is a good starting point, if you haven't read anything by him before.