The Word of God was created by an alien from another dimension known as the Author many ages ago. The book possessed words with the power to create and destroy. It was mistakenly left on ancient Earth by its creator and found by humans who considered the book the Word of God because of the power of the words. Mystics who studied the book discovered the words should be used sparingly or they would risk the Author hearing them. Those who spoke the words of the book would have the words carved into their bones which acted as a mark which the Author could use to control them.
Isaac Newton desperately sought the book and its power during his tenure as Sorcerer Supreme, unaware of the book's true nature and origin. He eventually obtained it and planned on using its power to become a god at the opposition of his fellow Sorcerers Supreme. However, Newton's excessive use of the words eventually summoned the Author who reclaimed the book and subsequently attempted to destroy the Earth. The book was eventually destroyed when Doctor Strange tricked the Author into destroying its own book.