This story is about the horribly stupid Thursday and its extraordinary consequences, and why the universe is a lot safer when we have a towel.
This story is also about a book entitled: GALAXIS Guide for Hitchhikers. This is not an earthly book, it was never published on Earth, and before the terrible catastrophe no Earthling had seen or heard of it.
The book is nonetheless remarkable. This is probably the most remarkable book that has seen the light of day in the care of the giant publishing houses of Kisgöncöl - although the earthlings have not even heard of them.
This book is not only unheard of, but amazingly successful. It's more popular than the Heavenly Household Omniscient, better selling than the illustrated publication Sixty-Three More Figures in the Case of Weightlessness, and more controversial than Oolon Coluphid's philosophical bombshell trilogy: Where God Went Wrong, Some of God's Worst Mistakes, and Who Is It After All Is God At All?
For some of the more liberal civilizations of the Outer Eastern Rim of the Galaxy, the GALAXIS Guide has already supplanted the mighty Encyclopaedia Galactica, and alone fulfills the role of the repository of all knowledge and wisdom, because although it is full of gaps and full of dubious, or at least blatantly inaccurate data, two in an important respect, it surpasses its less soaring predecessor.
On the one hand, it is somewhat cheaper. On the other hand, the following words can be seen on the cover, in nice big letters:

DO NOT PANIC!