I think an American, not throughly immersed in English culture, humor etc. might find the book bizarre, even a bit daft, on first reading.
A side note: I should not write small treatises on literature, culture, humor, opinion, or Adams with such a high level of blood in my coffee stream :D
Huh. I had never realized the radio play came first! Ya learn something every day...
Now I don't feel so bad about having only heard the play...