Hitchhiker's, volume 1.
Earth is destroyed to make way for a bypass. Fortunately for Arthur Dent, his friend Ford Prefect turns out to be an alien and manages to escape, with Arthur.
The plot is not bad, but it's the writing that is fantastic:
Vogon ships "hung in the sky in exactly the way bricks don't".
The Hooloovoo is a super-intelligent shade of the colour blue.
The old man who said nothing was true but was later found to be lying.
"After a second or so, nothing continued to happen".
"This must be Thursday. I never could get the hang of Thursdays" (borrowing from Truman Capote's "Breakfast at Tiffany's).
"Bits of it were dullish grey. Bits of it were dullish brown. The rest of it was rather less interesting". "An acute attack of no curiosity".
"Almost, but not quite, entirely unlike tea".
"It's unpleasantly like being drunk. What's so bad about being drunk? Try asking a glass of water."
God refuses to prove he exists because proof denies faith and without faith he is nothing. But the Babel fish is a dead giveaway - so God disappeared in a puff of logic.
Infinite improbability drive.
Brief summary and favourite quotes from the other four of the five books, as follows:
Restaurant at the End of Universe (vol 2): http://www.goodreads.com/review/show/107768059
Life, the Universe and Everything (vol 3):
So Long, and Thanks for all the Fish (vol 4): http://www.goodreads.com/review/show/107768203
Mostly Harmless (vol 5): http://www.goodreads.com/review/show/107768298