How Important is the Old Testament to the Book of Revelation?

It is very important. Some would say that the Old Testament appears in imagery as well as quotation and allusion more in the book of Revelation than in any other book in the Bible. Many think that the apostle John wrote both the Gospel of John and Revelation. In John 1:1 the apostle begin his epistle by developing Genesis 1:1, and this correlation continues in the subsequent verses. John loved the Old Testament and made it a part of his presentation of Jesus. The same is true of the book of Revelation.