JUST STARTING OUT:
The ESV Study Bible by Crossway
Includes a 10 page introduction to Revelation and verse by verse commentary. A great resource for the whole Bible.
How to Read the Bible For All its Worth by Gordon Fee & Douglas Stuart
This is very readable and a good introduction to the basic principles for understanding Revelation. If you've never read Revelation or other books dealing with Revelation, start here.
The Returning King by Vern Poythress
This book is an easy introduction to the book of Revelation, written in a simple, even humorous style. Best of all: it is available for FREE on his website: http://www.frame-poythress.org/ebooks/the-returning-king/
The Message of Revelation by Michael Wilcock (BST Series)
Wilcock gives us a very accessible commentary on the whole of Revelation which deals openly and honestly with the difficulties and differences. This is a good guide to anyone who is attempting Revelation seriously for the first time.
Revelation: the Spirit speaks to the churches by James Hamilton
A slightly thicker volume compared to Wilcock, but it is very accessible and helpful. Each chapter focusses on a new section of Revelation and is written in the form of a sermon - which might frustrate some more serious readers, but will help those starting out.
The Book of Revelation (NIGTC Series) by G.K. Beale
Beale's commentary on Revelation is grounded in the Old Testament and will challenge and inform. It is a larger and more detailed volume that will probably interest students and pastors more.
The Theology of the Book of Revelation by Richard Bauckham
The Theology of the book of Revelation is a goldmine of insights into the book . Readers are richly rewarded with insights on how the original listeners of the Revelation letter would have been impacted by the book. This is not a commentary.
Revelation: Four Views by Steve Gregg
A Parallel Commentary covers the traditional views in an even-handed fashion. Four parallel columns present the information you need on these key views, and inform you about outstanding commentators on the book of Revelation. No other book gives such extensive coverage of how the church has understood Revelation over the centuries.
Reading Revelation Responsibly by Michael Gorman
Gorman writes with a very informal style, which makes the book an easy read. What makes the book useful is Gorman insistence that the book be taken for what it is: a Revelation of Jesus Christ which should have a profound impact on how we live. Not recommend as a first read, but to those preaching through Revelation it might just help to keep the main thing the main thing: the Lamb who was slain.
The Book of Revelation (NICNT series) by Robert H Mounce
Clear and very comprehensive commentary. He interacts with the traditional interpretations very well, so that the reader gets acquainted with the landscape of diversity in interpretation.
For those who were challenged by Bradley Trout's Greek insights, have a look at 'Basics of Biblical Greek' by William Mounce.
Courses available online at: https://www.teknia.com/classes