Douglas Adams: Life the Universe and Everything (Douglas Adams: Life the Universe and Everything #3)

In consequence of a number of stunning catastrophes, Arthur Dent is surprised to find himself living in a hideously miserable cave on prehistoric Earth. However, just as he thinks that things cannot get possibly worse, they suddenly do. He discovers that the Galaxy is not only mind-boggingly big and bewildering but also that most of the things that happen in it are staggeringly unfair.

Escaping the end of the world for a second time, Arthur, Ford, and their old friend Slartibartfast embark (reluctantly) on a mission to save the whole galaxy from fanatical robots. Not bad for a man in his dressing gown...