How do we know that the book in Revelation 10 is the Bible?

In Revelation 10, the 'little book' is described as being open in the hand of the mighty angel, which signifies the opening of God's Word to His people. The term used for this book, 'Biblioridion,' is unique to this chapter and distinguishes it from other texts in the New Testament. The open nature of the book indicates that previously, during the days of darkness and ignorance, particularly under the papal authority, the Word of God was hidden. With the Reformation, the Scriptures were made available, revealing the sweetness of God's promises and truths to believers.