Contained inside are all the secrets of Gummi wisdom and tradition, including spells, recipes, technical schematics and the complete history of the Gummi Bears. It can only be unlocked by a Gummi Medallion.
Despite it being a magical book, it is still fragile to certain things that could damage a normal book. In the episode "The Road to Ursalia", it was accidentally burnt to ashes by a candle left by Gruffi. Gruffi when the city of Ursalia to find a replacement, but was unsuccessful. However, he was given a magic bookmark by Sir Thornberry there that enables the Great Book to be completely restored.
The book was originally locked up centuries by the great Gummis and rested in the study of Gummi Glen in the care of the six remaining Gummis, Zummi, Grammi Gummi, Sunni, Tummi, Gruffi and Cubbi Gummi. The book was finally reopened by a Gummi Medallion once belonging to Cavin when he angrily threw it away. The first page shown was a message left behind possibly by the ancient Gummis and then vanished after reading it.
The message encouraged the Gummi's of Gummi Glen to come out of hiding and help Cavin stop Duke Igthorn from destroying Dunwyn Castle and since then they continue performing brave and honorable deeds which they record in the book.
One time Gruffi researches the book on how to repair things. He left a candle there and then the Great Book burned to ashes. It was then restored by a magic Bookmark given by Sir Thornberry to Gruffi when he comes to Ursalia to find a replacement.