The Hitchhiker's Guide To The Galaxy (book 1), Douglas Adams

It's an ordinary Thursday lunchtime for Arthur Dent until his house gets demolished.

The Earth follows shortly afterwards to make way for a new hyperspace express route, and his best friend has just announced that he's an alien. At this moment, they're hurtling through space with nothing but their towels and an innocuous-looking book inscribed, in large friendly letters, with the words: DON'T PANIC. The weekend has only just begun .