The Book of Overcoming Apophis is a common Ancient Egyptian spellbook that contains spells for fighting Apophis during Ra's nightly journey through the Duat. According to JD Grissom, they are not actually very effective against Apophis in reality due to his great power. The evil magician Setne wrote a version of the book where he recorded his spell for capturing a sheut and his shadow execration. He wrote six copies of the book that were in Nomes and museums all over the world.
While searching for a way to defeat Apophis, Brooklyn House librarian Cleo discovers that he is destroying Nomes that have copies of the Book of Overcoming Apophis that was written by Setne. Carter and Sadie realize that Apophis must be destroying them as they contain a secret weakness of his and try to protect the last copy. However, Apophis destroys the last copy and the Fifty-First Nome without them finding out what it contains though they manage to save King Tut's shadow box which Setne tells Sadie will be a clue to what was in the book. They are later able to piece together that the information in the book was about capturing and execrating shadows to destroy a being and both Thoth and Setne confirm that Setne had written the spells he had created for that purpose in the Book of Overcoming Apophis. While the book is gone, with the help of Setne and the Book of Thoth, Carter and Sadie are still able to find the spell and use it to destroy Apophis.