There is one main book titled Good Omens: The Nice and Accurate Prophecies of Agnes Nutter, Witch. This book was written by Neil Gaiman and Terry Pratchett. It was first published in 1990 and has since become a beloved classic in the fantasy genre.
While there is only one main book, the story has inspired various adaptations, including a television series. The book itself is a standalone novel, and no direct sequels have been written by the original authors. However, the rich world and characters have left a lasting impact, leading to continued interest and discussions among fans.