For a better understanding of the structure and outline of Revelation, we would recommend watching the Bible Project videos on Revelation (https://youtu.be/5nvVVcYD-0w & https://youtu.be/QpnIrbq2bKo)

An accessible commentary for most readers is Vern Poythress’ The Returning King. Also of use is Michael Gorman’s Reading Revelation Responsibly. The entry on Revelation in A Biblical-Theological Introduction to the New Testament: The Gospel Realized is helpful, as is the commentary in the Tyndale New Testament Commentary series by Ian Paul.

If you are particularly interested in digging further into the symbolism and Old Testament imagery of Revelation, G. K. Beale’s Revelation: A Shorter Commentary is a great place to start. More adventurous readers could explore his longer work, or Peter Leithart’s recent volumes in the International Critical Commentary series.