Robert M. Grant , A Historical Introduction to the New Testament, , Chapter 15: The Book of Revelation
We should conclude that the book was written or dictated by an early and significant John, perhaps the son of Zebedee. Two important features of this book are the End Times which dominates it, and the use, throughout the writing, of hymn-like materials.
Richard Heard , An Introduction to the New Testament, , Chapter 24: The Study of The Revelation;
Was the eschatological expectation of Jesus expressed in the crude material forms of contemporary Jewish apocalyptic, or do such passages in the gospels represent the distortion of his original message under the influence of Christian prophecy?
Richard Heard , An Introduction to the New Testament, , Chapter 25: The Revelation of John;
There is no 'teaching' as such in the Revelation. Even in the letters to the churches it is not teaching which is given, but commands from the Spirit, and the main purpose of the book as a whole is the revelation of the future.