So Long and Thanks For All The Fish

This book is by Douglas Adams. Arthur is back on the Earth but it hasn't been destroyed. He is back in his house and apparently 5 years have passed. he meets this girl who has gone mad and thinks the earth is destroyed. A couple months later he sees the same girl hitchhiking and picks her up. He ends up Finding Ford Prefect And Ford, Arthur, and the girl Fenchurch, hitch a ride on a spaceship and go to this planet where There is a message that says I am sorry for the inconvenience and the book ends here with Arthur and Fenchurch carrying Martin who is nearly dead.