This book should be read after the "The hitchhiker's Guide to the Galaxy", due to the fact that "The Restaurant at the End of the Universe" starts where the previously mentioned book ends. That is, with the two survivors to the Earth's destruction, Arthur Dent and Ford Prefect, traveling along Trillian, Marvin the robot and Zaphod Beeblebrox in the "Heart of gold", a stolen Improbability Drive ship.
If you read this book, you will go along with our friends in their adventures, for example when they visit Milliways, the Restaurant at the End of the Universe, or when they escape certain destruction in a stuntship used by rockstars. You will also learn the real meaning of "dying for a cup of tea", and have a chance to eat meat that wants to be eaten. Of course, Marvin will continue giving you lessons in pessimism, and Zaphod will go on being "so weird that he should be in movies".
I liked this book, but I didn't love it nearly as much as "The hitchhiker's Guide to the Galaxy". What is more, "The Restaurant at the End of the Universe" doesn't have a clear ending, and I find some fault in that. Of course, I am more than ready to read the next book in the series, but that is not the point.
On the whole, I don't recommend "The Restaurant at the End of the Universe" to those that haven't read "The hitchhiker's Guide to the Galaxy", due to the fact that they won't enjoy it so much. Notwithstanding that, I do recommend this book as entertaining reading material for those already addicted to Douglas Adams quirky sense of humour. It is not perfect, but it is more than good enough to enjoy :)